MB vs GB vs TB: Understanding Digital Storage Sizes

Q: How many MB are in a GB?

There are 1,024 MB (megabytes) in 1 GB (gigabyte) when using the binary system, which is how operating systems and most software measure storage. However, hard drive and SSD manufacturers use the decimal system, where 1 GB = 1,000 MB. This is why a '500 GB' hard drive shows less space than expected in Windows or macOS.

Q: How many GB are in a TB?

There are 1,024 GB (gigabytes) in 1 TB (terabyte) in binary measurement. In decimal measurement (used by drive manufacturers), 1 TB = 1,000 GB. So a '1 TB' hard drive will appear as approximately 931 GB in Windows or macOS, which uses binary measurement.

Q: What is the difference between MB and GB?

A megabyte (MB) is 1,024 times smaller than a gigabyte (GB). In practical terms: a typical MP3 song is 3–5 MB, a standard-definition movie is 700 MB–1 GB, and a high-definition movie is 4–8 GB. Use MB for small files and GB for larger files, apps, and storage capacity.

Q: Is 1 GB equal to 1,000 MB or 1,024 MB?

It depends on the context. In binary (base-2) measurement — used by operating systems — 1 GB = 1,024 MB. In decimal (base-10) measurement — used by storage manufacturers — 1 GB = 1,000 MB. The IEC introduced the terms gibibyte (GiB) for the binary 1,024 MB to reduce confusion, but most consumer products still use 'GB' for both.

Q: How much storage do I need: 128 GB, 256 GB or 512 GB?

128 GB is sufficient for light users who store mostly apps and documents with photos backed up to the cloud. 256 GB suits most users who keep photos, videos, music and apps on-device. 512 GB is best for power users, gamers, or those who shoot a lot of video. For reference, a 4K video minute is about 400 MB, a typical app is 50–200 MB, and 1,000 photos average around 3–5 GB.

Q: Why does my 1 TB hard drive show less than 1 TB in Windows?

Because hard drive manufacturers calculate 1 TB as 1,000 GB (decimal), but Windows uses binary measurement where 1 TB = 1,024 GB. A '1 TB' drive therefore appears as approximately 931 GB in Windows. This discrepancy increases with larger drives — a '4 TB' drive shows about 3.63 TB in Windows.

Q: How many photos fit in 1 GB?

Approximately 250–500 photos fit in 1 GB, depending on the resolution and format. A smartphone photo from a modern 12–48 MP camera is typically 2–5 MB in JPEG format. At 3 MB average, 1 GB holds around 333 photos. RAW format photos are much larger (15–40 MB each), so 1 GB holds only 25–65 RAW images.

Q: What comes after terabyte (TB) in storage size?

After terabyte (TB) comes petabyte (PB), then exabyte (EB), then zettabyte (ZB), then yottabyte (YB). Each step is 1,024× the previous in binary. In practical terms: 1 PB = 1,024 TB, which is used for large data centre storage. Consumer storage currently maxes out at around 20–24 TB for single hard drives.

Whether you’re buying a new phone, choosing a laptop hard drive, or trying to figure out whether your video will fit on a USB stick — understanding the difference between MB, GB, and TB is essential. This guide explains exactly what each storage unit means, how they relate to each other, why your hard drive always shows less space than advertised, and what real-world files actually look like in each unit.

The storage unit scale

Digital storage is measured in units based on bytes — the fundamental unit of digital information. From smallest to largest, the common storage units are:

Kilobyte

1,024 B

Megabyte

1,024 KB

Gigabyte

1,024 MB

Terabyte

1,024 GB

Petabyte

1,024 TB

Each unit is 1,024 times larger than the previous one in binary measurement. The reason it’s 1,024 (not 1,000) is that computers operate in base-2 (binary) — and 2¹⁰ = 1,024 is the closest power of 2 to 1,000.

MB, GB and TB defined

What is a megabyte (MB)?

A megabyte (MB) is 1,024 kilobytes (KB) in binary, or 1,000,000 bytes. It’s a relatively small storage unit by today’s standards — think of a single photo, a short MP3 song, or a simple document. For internet speeds and mobile data plans, megabytes are still a common reference point.

What is a gigabyte (GB)?

A gigabyte (GB) is 1,024 megabytes — about 1,073 million bytes. This is the standard unit for measuring smartphone storage, RAM, and most files you interact with daily. A modern phone typically starts at 64 GB or 128 GB of internal storage. A typical HD movie is 4–8 GB.

What is a terabyte (TB)?

A terabyte (TB) is 1,024 gigabytes — about 1 trillion bytes. Hard drives, SSDs, and external storage devices are commonly sold in terabyte increments: 1 TB, 2 TB, 4 TB, and so on. A 1 TB drive can hold roughly 250,000 average-quality photos, 250 HD movies, or tens of thousands of music tracks.

Full conversion chart

Complete reference table for converting between digital storage units (binary, as used by operating systems):

Unit	In bytes	In KB	In MB	In GB
1 KB	1,024 B	1	0.000977 MB	0.00000095 GB
1 MB	1,048,576 B	1,024 KB	1	0.000977 GB
1 GB	1,073,741,824 B	1,048,576 KB	1,024 MB	1
1 TB	1,099,511,627,776 B	≈ 1.07 billion KB	1,048,576 MB	1,024 GB
1 PB	≈ 1.13 quadrillion B	—	≈ 1.07 billion MB	1,048,576 GB

Real-world file size examples

Abstract numbers are hard to picture. Here’s what common files and content actually take up in storage:

📧

Plain text email

~5–20 KB

Without attachments. 1 MB holds thousands of emails.

🎵

MP3 song (3 min)

~3–8 MB

At 128–320 kbps bitrate. 1 GB ≈ 125–300 songs.

📸

Smartphone photo

~2–6 MB (JPEG)

RAW format is 15–40 MB per shot.

📱

Mobile app

~50–500 MB

Games can be 1–5 GB. Simple apps are often under 100 MB.

🎬

HD movie (1080p)

~4–8 GB

Streaming versions are compressed to 1.5–4 GB.

🎮

Modern PC game

~50–150 GB

Some AAA titles (e.g. Call of Duty) exceed 200 GB with updates.

📹

4K video (1 minute)

~350–500 MB

Uncompressed 4K is much larger — up to 12 GB per minute.

🖥️

Operating system

~25–40 GB

Windows 11 takes ~25 GB; macOS is around 12–35 GB installed.

Binary vs decimal: why your drive shows less space

This is one of the most common points of confusion in computing. When you buy a “1 TB” hard drive, it appears as only about 931 GB in Windows or macOS. Why?

Binary (OS) vs decimal (manufacturer)

Hard drive makers define 1 TB as exactly 1,000,000,000,000 bytes (10¹²). Operating systems define 1 TB as 1,099,511,627,776 bytes (2⁴⁰). The gap between these two numbers is what you “lose”.

Advertised size	Manufacturer bytes	OS display (binary)	Difference
500 GB	500,000,000,000 B	~465 GB	~35 GB
1 TB	1,000,000,000,000 B	~931 GB	~69 GB
2 TB	2,000,000,000,000 B	~1.82 TB	~180 GB
4 TB	4,000,000,000,000 B	~3.63 TB	~370 GB

No space is lost! The full storage space is physically there. It’s simply that the OS and manufacturer count bytes differently. The IEC created the terms gibibyte (GiB) and tebibyte (TiB) for binary measurement to reduce this confusion, but consumer products still predominantly use GB and TB for both systems.

How much storage do you need?

Choosing the right storage depends on how you use your device. Here’s a practical guide:

64 GB smartphone — Light users who stream music and video, use cloud storage for photos, and install a modest number of apps. Can fill up quickly if you shoot a lot of photos.
128 GB smartphone — The most common sweet spot for average users. Enough for thousands of photos, dozens of apps, and some offline media.
256 GB smartphone / laptop — For users who want to keep more content on-device, shoot video regularly, or install many large apps.
512 GB / 1 TB laptop SSD — For video editors, photographers, gamers, or anyone who works with large files. A full 4K video project can easily consume hundreds of gigabytes.
2 TB+ external drive — For long-term backups, archiving photos and videos, or storing large media libraries locally.

When planning storage, always leave at least 15–20% free space — operating systems and apps need breathing room to perform efficiently, and SSDs slow down noticeably when nearly full.

If you’re working with data transfer speeds as well as storage sizes, our digital storage converter also handles megabits vs megabytes — an important distinction for understanding broadband speeds, where ISPs measure in megabits per second (Mbps), not megabytes.

Convert MB, GB and TB instantly

Our free digital storage converter handles bytes, KB, MB, GB, TB and beyond — no maths needed.

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Frequently asked questions

How many MB are in a GB? +

There are 1,024 MB in 1 GB in binary measurement (used by operating systems like Windows and macOS). In decimal measurement (used by storage manufacturers), 1 GB = 1,000 MB. This is why a drive advertised as 500 GB shows ~465 GB in Windows — the OS uses binary, the manufacturer uses decimal. Use our digital converter to switch between all storage units.

How many GB are in a TB? +

There are 1,024 GB in 1 TB in binary (OS) measurement. In decimal (manufacturer) measurement, 1 TB = 1,000 GB. So a “1 TB” hard drive appears as approximately 931 GB in Windows, because the OS uses binary (1 TB = 1,024 GB) while the manufacturer uses decimal (1 TB = 1,000 GB).

What is the difference between MB and GB? +

A gigabyte (GB) is 1,024 times larger than a megabyte (MB). In everyday terms: a song is 3–5 MB, a photo is 2–6 MB, but a movie is 4–8 GB (4,000–8,000 MB). GB is used for hard drives, phone storage, and RAM. MB is used for individual files and small data transfers.

Is 1 GB equal to 1,000 MB or 1,024 MB? +

Both — it depends on the context. Operating systems use 1 GB = 1,024 MB (binary). Storage manufacturers use 1 GB = 1,000 MB (decimal). The IEC introduced “gibibyte (GiB)” for the binary value to reduce confusion, but the term “GB” is still used for both in most consumer contexts.

How much storage do I need: 128 GB, 256 GB or 512 GB? +

128 GB suits light users who rely on cloud storage. 256 GB is the sweet spot for most people — comfortable for thousands of photos, many apps, and some offline media. 512 GB is ideal for video creators, gamers, or anyone who keeps large files on-device. Remember: one minute of 4K video is ~400–500 MB, and one large game can be 50–150 GB alone.

Why does my 1 TB hard drive show less than 1 TB in Windows? +

Because the drive manufacturer counts 1 TB as 1,000,000,000,000 bytes (decimal), but Windows counts 1 TB as 1,099,511,627,776 bytes (binary). Dividing the manufacturer’s 1 trillion bytes by Windows’ definition gives ~0.909 TB (≈ 931 GB). No data is missing — it’s purely a difference in counting conventions. Use our storage converter to see the exact numbers.

How many photos fit in 1 GB? +

Approximately 200–500 photos fit in 1 GB, depending on the camera and file format. Modern smartphone photos in JPEG format average 3–5 MB each — at 4 MB average, 1 GB holds around 256 photos. RAW format photos (15–40 MB each) fit only 25–65 per GB. Enabling HEIF/HEIC format on iPhones can roughly double the number of photos compared to JPEG.

What comes after terabyte (TB) in storage size? +

The storage hierarchy after TB is: Petabyte (PB) = 1,024 TB → Exabyte (EB) = 1,024 PB → Zettabyte (ZB) = 1,024 EB → Yottabyte (YB) = 1,024 ZB. In practice, 1 PB is used for enterprise data centre storage. The entire internet is estimated to hold several zettabytes of data. Consumer drives currently max out at around 20–24 TB per drive.