KB vs MB vs GB vs TB
Updated April 28, 2026
Quick Answer
KB (kilobyte) is the smallest, TB (terabyte) is the largest of the four common storage units. In order from smallest to largest: KB → MB → GB → TB. Each step up is roughly 1,000 times larger than the one before it. A plain text email is measured in KB. A photo is measured in MB. A movie or your phone’s total storage is measured in GB. A hard drive or cloud backup plan is measured in TB. One important distinction: storage and internet speed use different units — file sizes use bytes (MB, GB) while connection speeds use bits (Mbps, Gbps). They are not directly comparable.
| Unit | Symbol | Approximate size | Real-world equivalent |
|---|---|---|---|
| Kilobyte | KB | 1,000 bytes | A short text email, a small Word document |
| Megabyte | MB | 1,000 KB | A smartphone photo, a 3-minute MP3 |
| Gigabyte | GB | 1,000 MB | An HD movie, a mobile app, 1 hour of 4K video |
| Terabyte | TB | 1,000 GB | A laptop hard drive, a full photo library |
Table of Contents
Why These Units Matter More Than Ever in 2026
According to IDC research cited by Rivery, the global datasphere stood at 149 zettabytes as of 2024 and is projected to reach 394 zettabytes by 2028. One zettabyte is one trillion gigabytes. These are numbers that require scientific notation to write comfortably — and the reason they exist is because billions of people are constantly creating, storing, and transmitting files measured in KB, MB, GB, and TB every single day.
Understanding storage units is no longer optional technical knowledge. It determines whether you buy the right phone, choose the right cloud storage plan, understand why your download is slower than expected, and recognize when a manufacturer is bending definitions to make a drive sound larger than your computer thinks it is.
This guide explains all of it — including a few things most explainers skip.
Start Here: Bits and Bytes
Before KB, MB, GB, and TB make sense, you need the two most fundamental units.
A bit is the smallest possible unit of digital data. It’s a single binary digit — either a 0 or a 1. Everything your computer does ultimately reduces to sequences of these two values. The word “bit” is short for binary digit.
A byte is 8 bits grouped together. One byte can represent one character of text in basic encoding — a letter, a number, a punctuation mark. When you type the word “hello,” that’s 5 bytes.
This distinction matters because storage and internet speed use different units:
- File sizes and storage capacity are measured in bytes — written with a capital B: KB, MB, GB, TB
- Internet speeds and data transfer rates are measured in bits per second — written with a lowercase b: Kbps, Mbps, Gbps
The confusion between these two systems is responsible for one of the most common tech frustrations people have — more on that in the download speed section below.
What Each Unit Actually Means
Kilobyte (KB) — Roughly 1,000 bytes
A kilobyte is the smallest storage unit you’ll encounter in everyday use. The prefix kilo means thousand, so a kilobyte is approximately 1,000 bytes (technically 1,024 in binary computing — we’ll explain the difference shortly).
What fits in a kilobyte:
- A single-page plain text document: ~2–5 KB
- A short email with no attachments: ~10–20 KB
- A contact in your phonebook: ~1–2 KB
- A small icon file: ~5–50 KB
Kilobytes were the defining storage unit of the personal computing era’s early days. A floppy disk — if you’re old enough to remember them — held 1.44 MB, or about 1,440 KB. That seemed like a lot at the time. Today, a single photo from your phone is 200–300 times larger than that.
In modern computing, you’ll see kilobytes used mainly for small files: configuration files, cookies, cached web data, and SMS text messages. When something is described in KB, it’s lightweight — the kind of file that transmits almost instantly even on a slow connection.
Megabyte (MB) — Roughly 1,000 KB
A megabyte is where most people’s day-to-day file interactions live. The prefix mega means million — so one megabyte is approximately one million bytes.
What fits in a megabyte:
- A JPEG photo from a smartphone camera: 3–8 MB (compressed)
- A RAW photo from a modern 50MP smartphone: 20–30 MB (uncompressed)
- A 3-minute MP3 music file: 3–5 MB
- A PDF document (10 pages, no images): ~1–3 MB
- One minute of standard voice call recording: ~1 MB
- An ebook: ~1–5 MB
What megabytes measure in context:
- Email attachment limits are typically set in MB (most email providers cap single attachments at 25 MB)
- Mobile data usage is often tracked in MB for lighter users
- App sizes on older or budget phones are displayed in MB
One hundred megabytes is roughly enough for 25 songs in MP3 format, or about 8–10 minutes of 1080p video, or 15–30 compressed smartphone photos.
Gigabyte (GB) — Roughly 1,000 MB
The gigabyte is the unit most people encounter most often. Phone storage, laptop RAM, internet data plans, video game downloads, cloud storage free tiers — GB is the language of modern consumer technology.
What fits in a gigabyte:
- Compressed 1080p HD movie (2 hours): 3–5 GB
- 4K movie (2 hours): 15–25 GB
- One hour of 4K footage shot on an iPhone: ~20–25 GB
- One hour of 4K footage at 60fps (ProRes): ~60–90 GB
- A typical mobile game (iOS/Android): 1–4 GB
- A major PC game (2026, base install): 50–150 GB
- Call of Duty (full install with all content): ~300 GB
- Android operating system: ~6–8 GB
- 200 smartphone photos (JPEG compressed): ~1 GB
Real-world GB context:
- Entry-level smartphones ship with 128 GB of storage — enough for thousands of photos, dozens of apps, and a few movies
- A basic mobile data plan offers 5–15 GB per month; a heavy streamer can burn through 15 GB in a single day
- Google Drive, iCloud, and OneDrive each offer 5–15 GB of free cloud storage — enough for a few months of phone backups before you hit the paywall
Terabyte (TB) — Roughly 1,000 GB
The terabyte is the unit of serious storage: full hard drives, NAS devices, professional video archives, and enterprise backups. Tera means trillion, so one terabyte is approximately one trillion bytes.
What fits in a terabyte:
- Compressed MP3 music files: ~250,000 songs
- JPEG smartphone photos: ~200,000–300,000 images
- 1080p HD movies: ~200–300 films
- 4K movies: ~40–60 films
- A standard laptop hard drive: 512 GB to 2 TB
- A desktop PC storage drive: 1–8 TB is common
- A consumer NAS (Network Attached Storage) device: 4–20+ TB
What 1 TB actually means in practice: If you shoot video as a hobby, a single day of 4K filming can generate 100–200 GB of footage. One terabyte fills up in roughly a week of serious shooting. Professional videographers and photographers typically need multiple drives or cloud storage plans measured in multiple terabytes.
The Complete Storage Reference Table (2026)
| File Type | Typical Size | How many fit in 1 GB? | How many fit in 1 TB? |
|---|---|---|---|
| Plain text email | 10–50 KB | 20,000–100,000 | 20 million+ |
| Word document (10 pages) | 50–200 KB | 5,000–20,000 | 5–20 million |
| Ebook (EPUB) | 1–5 MB | 200–1,000 | 200,000–1 million |
| Smartphone photo (JPEG) | 3–8 MB | 125–333 | 125,000–333,000 |
| Smartphone photo (RAW) | 20–30 MB | 33–50 | 33,000–50,000 |
| 3-minute MP3 song | 3–5 MB | 200–333 | 200,000–333,000 |
| FLAC (lossless audio track) | 25–50 MB | 20–40 | 20,000–40,000 |
| 1-hour podcast (compressed) | 30–60 MB | 17–33 | 17,000–33,000 |
| Standard-def movie (480p) | 700 MB–1.5 GB | ~1 | 700–1,400 |
| HD movie (1080p) | 3–6 GB | 0.2 | 167–333 |
| 4K movie (HDR) | 15–25 GB | — | 40–67 |
| Mobile app (typical) | 100–500 MB | 2–10 | 2,000–10,000 |
| PC game (mid-size) | 20–60 GB | — | 17–50 |
| PC game (AAA, 2025–26) | 100–300 GB | — | 3–10 |
| 1 hour of 4K iPhone video | 20–25 GB | — | 40–50 |
| 1 hour ProRes 4K video | 60–90 GB | — | 11–16 |
| AI-generated image (WEBP) | 200–800 KB | 1,250–5,000 | 1.25–5 million |
| AI-generated image (PNG) | 2–6 MB | 167–500 | 167,000–500,000 |
Note: All sizes are approximate ranges based on typical compression settings and content. Video sizes vary significantly depending on codec, bitrate, and resolution. Game sizes reflect installation size including updates as of early 2026.
The 1024 vs. 1000 Problem: Why Your “1 TB” Drive Shows 931 GB
This is the most common complaint in consumer storage — and the most consistently under-explained. You buy a 1 TB hard drive, plug it into your computer, and Windows reports 931 GB of available space. You didn’t get scammed. But you’re also not imagining the discrepancy. Here’s what’s actually happening.
Two different definitions of the same word
There are two legitimate ways to define a kilobyte, and the industry uses both — inconsistently and without ever telling you which one applies.
The decimal definition (base-10): Used by hard drive manufacturers and storage device makers. In this system, 1 kilobyte = exactly 1,000 bytes, 1 megabyte = exactly 1,000,000 bytes, and so on — clean powers of 10.
The binary definition (base-2): Used by operating systems like Windows. In this system, 1 kilobyte = 1,024 bytes (2¹⁰), because computers process data in powers of 2. This means 1 megabyte = 1,048,576 bytes, 1 gigabyte = 1,073,741,824 bytes.
The math behind the missing space
When a manufacturer labels a drive as “1 TB,” they mean 1,000,000,000,000 bytes in decimal. When Windows reads that drive, it divides by 1,024 three times (converting bytes to KB to MB to GB) — using the binary definition. Here’s the actual calculation:
1,000,000,000,000 ÷ 1,024 = 976,562,500 KB
976,562,500 ÷ 1,024 = 953,674 MB
953,674 ÷ 1,024 = 931.3 GB
Result: your 1 TB drive shows as 931 GB in Windows. The data is all there — every single byte that was advertised. Windows is just applying a different measurement standard.
How different operating systems handle this
- Windows uses binary values (÷ 1,024) but labels them as GB. This is technically incorrect, which is why the number looks “missing.”
- macOS switched to decimal values in 2009. So a Mac will show your 1 TB drive as 1.0 TB — matching what’s on the box.
- Linux typically uses binary values by default, similar to Windows.
The officially correct terminology (that nobody uses)
NIST, the US National Institute of Standards and Technology, defines the kilo/mega/giga/tera prefixes as strictly decimal (×1,000). The binary equivalents have their own official names: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB), tebibyte (TiB). A tebibyte (1,024 GiB) is what Windows shows when it says “931 GB.”
In practice, almost no consumer product uses these terms. Manufacturers sell “TB,” operating systems display “GB,” and users are left doing mental math. The takeaway: expect to see roughly 7–10% less usable space than advertised when viewing storage on Windows. For a 1 TB drive, that’s about 69 GB “missing.” For a 4 TB drive, it’s about 276 GB.
The formatted space problem stacks on top
It gets slightly worse. When you format a drive, the file system itself (NTFS, exFAT, APFS) reserves a small portion for its own overhead — typically 1–5% of total capacity. On a 1 TB drive showing 931 GB in Windows, the actual usable formatted space might be closer to 915–920 GB. None of this is lost data. It’s all accounted for by the file system managing the drive.
The Download Speed Trap: MB vs. Mbps
This confusion costs real time and causes real frustration — and it comes down to one letter.
MB (capital B) = megabytes = storage, file size
Mb (lowercase b) = megabits = internet speed
These are not the same unit. One byte equals eight bits. So any speed quoted in megabits per second needs to be divided by 8 to get the megabyte-per-second download rate you actually experience.
The formula:
Download time (seconds) = File size in MB × 8 ÷ Your speed in Mbps
Real examples
| Your plan | Actual download speed | Time to download a 5 GB (5,000 MB) movie |
|---|---|---|
| 25 Mbps | 3.1 MB/s | ~27 minutes |
| 100 Mbps | 12.5 MB/s | ~7 minutes |
| 250 Mbps | 31.25 MB/s | ~2.7 minutes |
| 1 Gbps (1,000 Mbps) | 125 MB/s | ~40 seconds |
The gap between what ISPs advertise and what users experience isn’t only about network congestion — it also comes from this unit mismatch. A “100 Mbps plan” sounds fast enough to download anything instantly. In practice it downloads at 12.5 MB/s — still fast, but not the speed the number suggests.
Why ISPs use Mbps instead of MB/s
Megabits-per-second makes internet plans sound faster. A 100 Mbps plan sounds better than a 12.5 MB/s plan, even though they’re identical. This is intentional marketing — there’s no regulation requiring ISPs to advertise in a more intuitive unit.
The FCC’s Broadband Data Collection tracks and publishes internet speed data in Mbps, which is the universal standard for network measurement. When you see speed test results — from tools like Fast.com (Netflix) or Speedtest.net — they report in Mbps. To convert to a usable download speed in MB/s, divide by 8.
The streaming consumption version
For streaming specifically, the relevant number is how many MB of data per hour a given quality level consumes:
| Streaming quality | Data per hour | On a 50 GB/month mobile plan… |
|---|---|---|
| SD (480p) | ~700 MB | ~71 hours per month |
| HD (1080p) | ~3–5 GB | ~10–17 hours per month |
| 4K (2160p) | ~7–25 GB | ~2–7 hours per month |
| Netflix 4K (max quality) | ~7 GB | ~7 hours per month |
This is why data plans that seem generous on paper can disappear in a week of casual 4K streaming. The distinction between bits and bytes is part of why it feels that way — your plan is quoted in gigabytes, your usage is driven by habits measured in megabytes-per-hour.
Beyond Terabytes: PB, EB, ZB, YB
The storage hierarchy doesn’t stop at terabytes. For data professionals, researchers, and anyone curious about where the scale goes from here:
| Unit | Symbol | Equal to | Context |
|---|---|---|---|
| Petabyte | PB | 1,000 TB | Google processes petabytes of search data daily. A single PB would hold ~500 million photos. |
| Exabyte | EB | 1,000 PB | The internet generates roughly 2.5 exabytes of data per day. |
| Zettabyte | ZB | 1,000 EB | The global datasphere: approximately 149 zettabytes as of 2024, per IDC research. One zettabyte is one trillion gigabytes. |
| Yottabyte | YB | 1,000 ZB | There is currently no storage device or system in existence that operates at yottabyte scale. It remains a theoretical unit. |
| Ronnabyte | RB | 1,000 YB | Added to the International System of Units in 2022. Purely scientific context. |
| Quettabyte | QB | 1,000 RB | The largest currently named unit. Also added to SI in 2022. Entirely theoretical for now. |
To put a zettabyte in human terms: IDC noted that storing 175 zettabytes on Blu-ray discs would produce a stack of discs tall enough to reach the Moon 23 times. The global datasphere is projected to reach 394 zettabytes by 2028 — driven by AI training data, IoT sensor output, video surveillance, and cloud infrastructure expansion.
Consumer storage will catch up slowly. The first consumer-grade 1 TB hard drive shipped in 2007. In 2026, 4 TB SSDs are routine and 20 TB HDDs exist. Consumer petabyte storage — a drive holding 1,000 TB — is still a decade away at current price trajectories. But the units are already in use at enterprise and research scale.
How Much Storage Do You Actually Need?
Understanding units is useful. Knowing which size to buy is the practical payoff. Here’s a straightforward guide by device type, based on how real people use these products in 2026.
Smartphone Storage
128 GB: The baseline for most users. Comfortably holds 2,000–3,000 photos, 30–40 apps, and a handful of offline downloads. Gets tight if you shoot a lot of video.
256 GB: The sweet spot for most people. If you shoot video regularly, use your phone as a camera, or keep a large music library offline, start here. You’re unlikely to feel cramped within a 2-year phone cycle.
512 GB: For power users, photographers, and videographers who shoot 4K regularly. At 20–25 GB per hour of 4K footage, 512 GB is still only 20+ hours of raw video — less than it sounds for heavy shooters.
1 TB (now available on flagship phones): Almost exclusively for professionals who shoot ProRes video on their phone. Most users will never fill 512 GB before they upgrade.
The cloud trap: Don’t rely on “20 GB of iCloud storage” as a substitute for local storage. Cloud backup is not the same as local storage — cloud access requires connectivity, and the free tiers (5–15 GB) fill faster than most people expect. iCloud’s free 5 GB tier fills in approximately 1,500 iPhone photos at full resolution.
Laptop Storage
256 GB SSD: Entry-level and increasingly inadequate. Fine for light users (browsing, documents, streaming) who keep everything in cloud storage. A single AAA game install or video editing project can consume this entirely.
512 GB SSD: A reasonable starting point for most laptop buyers. Enough for the operating system (8–20 GB), productivity apps, personal files, and light media use without constant cloud management.
1 TB SSD: The practical choice for anyone who edits photos or video, plays PC games, or works with large files. One major game can exceed 100 GB — three or four games plus your applications and documents start filling 512 GB faster than expected.
2 TB SSD: For video editors, 3D artists, and anyone who keeps a local media library. At this size, storage is rarely the day-to-day constraint.
External drives as overflow: A 4 TB external hard drive can be purchased for under $80 in 2026. For most people, a 1 TB internal SSD plus a 4 TB external for media, photos, and backups is the most cost-effective combination.
Cloud Storage Plans
| Provider | Free storage | First paid tier | Sweet spot tier |
|---|---|---|---|
| Google One | 15 GB | 100 GB – ~$2.99/mo | 2 TB – ~$9.99/mo |
| iCloud+ | 5 GB | 50 GB – $0.99/mo | 2 TB – $9.99/mo |
| OneDrive | 5 GB | 100 GB – $1.99/mo | Microsoft 365 (1 TB) – $6.99/mo |
| Dropbox | 2 GB | 2 TB – $11.99/mo | 3 TB – $19.99/mo |
| Backblaze | — | Unlimited (computer backup) – $9/mo | Best value for whole-computer backup |
The honest advice: For most people, 2 TB of cloud storage ($9.99/month at Google or Apple) is more than enough for a lifetime of photos and documents. If your primary concern is backing up your whole computer rather than accessing files across devices, Backblaze’s flat-rate unlimited computer backup at $9/month is a category of its own — it doesn’t care about GB, it just backs up everything on your machine.
Home Media / NAS
If you store a local media library — ripped Blu-rays, downloaded films, home videos — you’ll burn through storage quickly. A single 4K Blu-ray rip can be 50–80 GB. A collection of 200 4K films occupies roughly 10–16 TB.
Entry NAS (4–8 TB): Adequate for most home users with a few hundred movies, a large music library, and years of photos.
Mid-range NAS (12–20 TB): For serious media collectors, content creators with large project archives, or small home offices needing shared network storage.
Enterprise/prosumer NAS (40 TB+): For video production studios, photographers with decades of raw files, or surveillance setups retaining 30+ days of 4K footage.
Frequently Asked Questions
Which is bigger — KB, MB, GB, or TB?
TB is the largest. In order from smallest to largest: KB (kilobyte) → MB (megabyte) → GB (gigabyte) → TB (terabyte). Each is approximately 1,000 times larger than the one before it.
How many MB are in a GB?
1,000 MB in a GB using the decimal definition (used by manufacturers and most everyday contexts). In binary computing (how most operating systems count): 1 GB = 1,024 MB. For most practical purposes, use 1,000.
How many GB are in a TB?
1,000 GB in a TB by the decimal standard (manufacturer labeling). In binary: 1 TB = 1,024 GB — which is why a 1 TB hard drive shows as approximately 931 GB in Windows (see the 1024 vs. 1000 section above).
Is MB bigger than GB?
No. GB is bigger than MB. 1 GB equals approximately 1,000 MB. GB is one full step up the scale. A movie file is measured in GB; a music file is measured in MB.
Why does my 1 TB hard drive only show 931 GB?
Your drive has exactly 1 trillion bytes — that’s what was advertised. The discrepancy comes from Windows using binary counting (dividing by 1,024 three times) while the manufacturer used decimal counting (multiples of 1,000). The calculation: 1,000,000,000,000 bytes ÷ 1,024 ÷ 1,024 ÷ 1,024 = 931 GB. All the storage is there; it’s a unit definition mismatch. macOS shows the correct “1 TB” because Apple switched to decimal display in 2009.
What’s the difference between MB and Mbps?
MB (megabytes) measures file size. Mbps (megabits per second) measures internet speed. There are 8 bits in a byte, so 1 Mbps = 0.125 MB/s. A 100 Mbps internet connection downloads at approximately 12.5 MB/s — not 100 MB/s. To convert your Mbps speed to MB/s: divide by 8.
How long does it take to download a 4K movie?
Roughly 3–7 minutes on a 100 Mbps connection. A 4K movie is typically 15–25 GB. At 12.5 MB/s (100 Mbps ÷ 8), that’s 1,200–2,000 seconds, or 20–33 minutes. On a 1 Gbps connection (125 MB/s): 2–3 minutes. Real-world times vary due to server speed and network congestion.
What’s the difference between storage and RAM?
Both are measured in GB. They’re both measured in GB but serve completely different functions. Storage (SSD, hard drive, cloud) holds your files permanently — it retains data when powered off. RAM (Random Access Memory) is your computer’s working memory — it holds data only while the system is running and is wiped when you shut down. More RAM makes your computer faster at multitasking; more storage means you can keep more files. A modern laptop might have 16 GB of RAM and a 1 TB SSD — both measured in GB, but not interchangeable.
What’s a petabyte, and when would I encounter one?
A petabyte (PB) is 1,000 terabytes. You won’t encounter petabytes in consumer devices — yet. Large organizations, data centers, research institutions, and cloud providers operate at petabyte scale. Google, for instance, processes petabytes of search data daily. The FBI’s DNA database, US Library of Congress digital archives, and large scientific projects like the Large Hadron Collider all operate at multi-petabyte scale.
How much is 1 GB of mobile data?
1 GB of mobile data allows approximately: 5 hours of SD video streaming, 1 hour of HD video streaming, 15 minutes of 4K streaming, 200 photos uploaded to the cloud, 10 hours of music streaming (Spotify, at standard quality), or about 500 casual web browsing sessions. The variance is wide because different activities consume data at very different rates. Video — especially 4K video — is by far the largest mobile data consumer.
Is 256 GB enough for a laptop?
It depends on your use case. For basic users (web browsing, email, office apps, cloud storage), 256 GB is sufficient. For gamers, video editors, photographers, or anyone who stores large files locally, 256 GB is likely to feel cramped within a year. The sweet spot for most users in 2026 is 512 GB to 1 TB.
What’s bigger: a zettabyte or a terabyte?
A zettabyte is astronomically larger. 1 zettabyte = 1,000 exabytes = 1,000,000 petabytes = 1,000,000,000 terabytes — one billion terabytes. The entire global datasphere — every piece of digital data created and stored worldwide — is measured in zettabytes. Your home storage is measured in terabytes. The ratio between a terabyte and a zettabyte is the same as the ratio between 1 meter and 1 billion kilometers.
The One-Paragraph Summary
KB is the smallest commonly used storage unit, TB is the largest. The correct order is KB → MB → GB → TB, with each step roughly 1,000 times larger than the last. File sizes use bytes (capital B); internet speeds use bits (lowercase b) — divide your Mbps speed by 8 to get your real download speed in MB/s. When your 1 TB drive shows as 931 GB in Windows, nothing is missing — it’s a unit definition difference between manufacturers (who use 1,000) and operating systems (which use 1,024). For storage shopping: 256 GB is fine for light laptop users, 512 GB is the sweet spot, 1 TB is for power users; on phones, 128 GB is baseline, 256 GB is comfortable, 512 GB is for heavy video shooters.
About This Article
This article was written by Alex Rivera, who covers tech explainers, consumer electronics, and digital lifestyle topics for Axis Intelligence. It was last verified against current storage device specs, operating system behavior, and pricing in April 2026.
Consumer tech & culture writer. 200+ gadget reviews. Covers phones, laptops, gaming, streaming, puzzles, and digital culture. Writes for real people buying real products.