In the decimal (SI) standard: 1 GB = 1,000 MB exactly. In the binary (IEC) standard: 1 GiB = 1,024 MiB. If you are calculating storage capacity, internet data plans, or file sizes as reported by most software, use 1 GB = 1,000 MB. If you are working with OS-level binary reporting, use 1 GiB = 1,024 MiB.

A petabyte (PB) is 1,000,000,000,000,000 bytes in the decimal system (10¹⁵ bytes, or 1,000 TB). In binary, the equivalent is a pebibyte (PiB) = 2⁵⁰ bytes ≈ 1.126 PB. To put it in perspective: Google processes approximately 20 petabytes of data per day, and the entire printed collection of the US Library of Congress is estimated at around 10 TB — meaning 1 PB could hold about 100 Libraries of Congress.

File Size Converter — Bytes, KB, MB, GB, TB (Binary & Decimal)

Q: Why does my 1 TB drive show only 931 GB?

Storage manufacturers measure 1 TB as 1,000,000,000,000 bytes (decimal/SI). Your operating system, however, reports sizes in binary (IEC) — where 1 GiB = 1,073,741,824 bytes. Dividing 1,000,000,000,000 by 1,073,741,824 gives approximately 931 GiB, which Windows and older macOS show as 'GB'. There is no missing storage — it is purely a difference in counting standards.

Q: What is the difference between a bit and a byte?

A bit is the smallest unit of digital data — it holds a single binary value of 0 or 1. A byte is a group of 8 bits. Bytes are used to measure file and storage sizes, while bits are commonly used to express network and internet speeds (Mbps, Gbps). For example, a 100 Mbps internet connection transfers 100 million bits — or about 12.5 megabytes — per second.

Q: What is the difference between MB and MiB?

MB (Megabyte) is the decimal/SI unit equal to 1,000,000 bytes (1,000²). MiB (Mebibyte) is the binary/IEC unit equal to 1,048,576 bytes (1,024²). The difference is roughly 4.86%. While everyday usage often says 'MB', operating systems traditionally report in MiB. The IEC introduced the kibibyte/mebibyte/gibibyte naming in 1998 to eliminate the ambiguity.

Q: Why do internet speeds use bits while storage uses bytes?

Internet speeds (Mbps, Gbps) use bits because the original telecommunications standards measured transmission rates in bits per second. Storage media (MB, GB) uses bytes because early computer architectures grouped bits into 8-bit bytes for data processing. When comparing download speed to file size, remember to divide Mbps by 8 to get megabytes per second (MBps). A 100 Mbps connection downloads a 500 MB file in about 40 seconds.

Q: Should I use binary or decimal for file size conversion?

Use decimal (SI) when: reading hard drive or SSD manufacturer specs, checking internet data plan limits, or working with cloud storage quotas — these all use powers of 1,000. Use binary (IEC) when: reading file sizes reported by Windows (which calls GiB 'GB'), working with RAM specifications, programming in low-level languages, or comparing OS-reported disk usage to manufacturer specs. When precision matters, always state whether you mean MB (decimal) or MiB (binary).

Standard:

Enter Value

From Unit

Try Examples:

Conversion Results Decimal (SI, 1000-based)

Unit	Value

Binary vs. Decimal — Two Ways to Count

Decimal (SI) — Storage Manufacturers

1 KB = 1,000 B

1 MB = 1,000,000 B

1 GB = 1,000,000,000 B

Powers of 10 (10³ per step)

Binary (IEC) — Operating Systems

1 KiB = 1,024 B

1 MiB = 1,048,576 B

1 GiB = 1,073,741,824 B

Powers of 2 (2¹⁰ per step)

Why your 1 TB drive shows 931 GB

The drive manufacturer counts 1 TB = 1,000,000,000,000 bytes. Windows reports in binary: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB (shown as "GB"). No storage is missing — it's purely a counting difference.

Common File Size Reference

Real-world sizes

File Type	Typical Size	Notes
Plain text email	5–20 KB	Without attachments
MS Word document (10 pages)	50–200 KB	Text only, minimal formatting
JPEG photo (smartphone)	2–6 MB	12–48 MP, high quality
RAW photo (DSLR)	20–50 MB	Uncompressed, 20–50 MP
MP3 song (3–4 min)	3–8 MB	128–320 kbps bitrate
FLAC song (lossless)	25–50 MB	CD-quality, no compression loss
HD (1080p) movie	4–8 GB	H.264/H.265, ~2 hours
4K UHD movie	50–100 GB	Blu-ray quality, HDR
DVD (single-layer)	4.7 GB	Standard DVD-5 capacity
Blu-ray disc	25–50 GB	Single/dual-layer
Mobile app install	50–500 MB	Varies widely by app
AAA video game	50–150 GB	Modern console/PC titles
Windows 11 ISO	~5.1 GB	Installer image
Ubuntu Linux ISO	~1.5 GB	Desktop edition

How the Conversion Works

All values are first converted to bits (the smallest unit), then divided by the target unit's factor. This ensures precision across any combination of units.

Decimal (SI) Formulas

1 Byte = 8 bits

1 KB = 1,000 bytes = 8,000 bits

1 MB = 1,000 KB = 10⁶ bytes

1 GB = 1,000 MB = 10⁹ bytes

1 TB = 1,000 GB = 10¹² bytes

1 PB = 1,000 TB = 10¹⁵ bytes

1 EB = 1,000 PB = 10¹⁸ bytes

Binary (IEC) Formulas

1 Byte = 8 bits

1 KiB = 1,024 bytes = 8,192 bits

1 MiB = 1,024 KiB = 2²⁰ bytes

1 GiB = 1,024 MiB = 2³⁰ bytes

1 TiB = 1,024 GiB = 2⁴⁰ bytes

1 PiB = 1,024 TiB = 2⁵⁰ bytes

1 EiB = 1,024 PiB = 2⁶⁰ bytes

Worked Example: Convert 1 GB to MB

Decimal: 1 GB = 1,000 MB (manufacturers, cloud storage)
Binary: 1 GiB = 1,024 MiB (OS memory addressing)
Mixed reality: A "1 GB" file on a decimal filesystem = 0.9313 GiB in binary = 953.67 MiB

What is a File Size Converter?

A file size converter is a tool that translates digital storage measurements from one unit to another — for example, converting gigabytes to megabytes, terabytes to gigabytes, or bytes to kilobytes. Every digital file occupies a specific amount of space, expressed in units built on the fundamental bit. File size converters are essential for comparing hard drive specs, estimating download times, managing cloud storage quotas, checking email attachment limits, and understanding operating system disk reports.

This converter supports two distinct standards — decimal (SI, powers of 1,000) and binary (IEC, powers of 1,024) — and shows all unit equivalents simultaneously for maximum convenience.

Binary vs. Decimal: Why Sizes Differ

The confusion between binary and decimal file sizes stems from two legitimate but incompatible counting systems. Computer engineers in the 1950s naturally used powers of 2 (binary), so 1 kilobyte meant 2¹⁰ = 1,024 bytes. Meanwhile, the International System of Units (SI) defines "kilo" as exactly 1,000. Storage manufacturers, following SI, label drives in powers of 1,000 to make their products appear larger.

The result: a "1 terabyte" hard drive actually stores 1,000,000,000,000 bytes by the manufacturer's count, but your operating system divides that by 1,073,741,824 (2³⁰) and reports 931.32 GiB — displayed as "931 GB" in Windows. No space is missing; the two systems simply count differently. In 1998, the IEC introduced unambiguous binary prefixes — kibibyte (KiB), mebibyte (MiB), gibibyte (GiB) — to eliminate this ambiguity, though everyday usage still widely uses KB/MB/GB for both.

Common File Size Units Explained

Bit (b): The smallest unit of digital information — a single 0 or 1. Network speeds are measured in bits per second (Mbps, Gbps).
Byte (B): 8 bits. The basic unit for file and storage sizes. A single ASCII character is 1 byte; a UTF-8 character can be 1–4 bytes.
Kilobyte (KB) / Kibibyte (KiB): 1,000 or 1,024 bytes. Typical for small text files, emails, and images.
Megabyte (MB) / Mebibyte (MiB): ~1 million bytes. Standard for photos, songs, and documents.
Gigabyte (GB) / Gibibyte (GiB): ~1 billion bytes. The everyday unit for apps, movies, and USB drives.
Terabyte (TB) / Tebibyte (TiB): ~1 trillion bytes. Common for hard drives, NAS devices, and cloud storage plans.
Petabyte (PB) / Pebibyte (PiB): ~1 quadrillion bytes. Data-center and cloud provider scale. Facebook stores hundreds of petabytes of photos.
Exabyte (EB) / Exbibyte (EiB): ~1 quintillion bytes. Internet traffic and national data infrastructure scale. The entire internet processes roughly 5 exabytes of data per day.

Why Storage Manufacturers Use Decimal but OS Uses Binary

Hard drive and SSD manufacturers advertise capacity in SI decimal units (GB = 10⁹ bytes) because it allows them to show larger numbers — 1,000,000,000 bytes sounds bigger than 931 GiB. This is legal and standardised under SI definitions.

Operating systems (Windows, older macOS, Linux) traditionally reported sizes in binary units because CPU addressing, RAM allocation, and filesystem block sizes are all power-of-2 based. Modern macOS (since 10.6 Snow Leopard, 2009) switched to decimal reporting, so a 1 TB drive shows as ~1 TB in macOS but ~931 GB in Windows — even though the physical capacity is identical.

File Size Tips for Developers and Everyday Users

For everyday users:

When comparing storage devices, use the manufacturer's GB (decimal) to compare like-for-like.
When Windows shows "931 GB free" on a "1 TB" drive, you have not lost storage — Windows is simply reporting in GiB.
To estimate download time: divide the file size in megabytes by your speed in megabytes/second (remember: 100 Mbps ÷ 8 = 12.5 MB/s).

For developers and sysadmins:

Always specify whether values are decimal or binary in documentation and APIs — use "MiB" and "GiB" when you mean binary to avoid ambiguity.
In programming, use 1 << 20 for 1 MiB (1,048,576) to avoid floating-point errors.
Cloud providers (AWS, GCP, Azure) typically use decimal GB/TB for billing — confirm before estimating costs.
Linux df and du commands report in 1K blocks by default; use -h for human-readable binary, or --si for decimal.

Frequently Asked Questions

Why does my 1 TB drive show only 931 GB?

Storage manufacturers measure 1 TB as 1,000,000,000,000 bytes (decimal/SI). Your operating system, however, reports sizes in binary (IEC) — where 1 GiB = 1,073,741,824 bytes. Dividing 1,000,000,000,000 by 1,073,741,824 gives approximately 931 GiB, which Windows and older macOS display as "GB". There is no missing storage — it is purely a difference in counting standards. macOS (since Snow Leopard 2009) switched to decimal reporting, so a 1 TB drive correctly shows ~1 TB.

What is the difference between a bit and a byte?

A bit is the smallest unit of digital data — it holds a single binary value of 0 or 1. A byte is a group of 8 bits. Bytes are used to measure file and storage sizes (KB, MB, GB), while bits are used to express network and internet speeds (Kbps, Mbps, Gbps). A lowercase "b" = bit; uppercase "B" = byte. A 100 Mbps internet connection transfers 100 million bits — or about 12.5 megabytes — per second.

What is the difference between MB and MiB?

MB (Megabyte) is the decimal/SI unit equal to 1,000,000 bytes (10⁶). MiB (Mebibyte) is the binary/IEC unit equal to 1,048,576 bytes (2²⁰). The difference is roughly 4.86%. While everyday usage often says "MB", operating systems traditionally report in MiB. The IEC introduced the kibibyte / mebibyte / gibibyte naming standard in 1998 to eliminate ambiguity between the two systems.

How many MB is 1 GB?

Decimal (SI): 1 GB = exactly 1,000 MB — used by hard drive manufacturers, cloud storage providers, and internet data plans.
Binary (IEC): 1 GiB = exactly 1,024 MiB — used in OS memory addressing and traditional filesystem reporting.

For most everyday purposes (storage, data plans), use 1 GB = 1,000 MB. For OS-level or programming contexts, 1 GiB = 1,024 MiB.

Why do internet speeds use bits while storage uses bytes?

Internet speeds (Mbps, Gbps) use bits because the original telecommunications standards measured transmission rates in bits per second — the signal-level unit. Storage media (MB, GB) uses bytes because early computer architectures grouped bits into 8-bit bytes for data processing and addressing. When comparing download speed to file size, divide Mbps by 8 to get megabytes per second (MBps). A 100 Mbps connection downloads a 500 MB file in about 40 seconds (500 ÷ 12.5 = 40 s).

What is a petabyte? How big is it?

A petabyte (PB) is 1,000,000,000,000,000 bytes in the decimal system (10¹⁵ bytes, or 1,000 TB). In binary, the equivalent is a pebibyte (PiB) = 2⁵⁰ bytes ≈ 1.126 PB. To put it in perspective:

Google processes approximately 20 petabytes of data per day.
The US Library of Congress print collection ≈ 10 TB → 1 PB could hold ~100 Libraries of Congress.
All human speech ever recorded is estimated at ~5 EB (5,000 PB).

Should I use binary or decimal for file size conversion?

Use decimal (SI) when: reading hard drive or SSD manufacturer specs, checking internet data plan limits, or working with cloud storage quotas — these all use powers of 1,000.

Use binary (IEC) when: reading file sizes reported by Windows (which calls GiB "GB"), working with RAM specifications, programming in low-level languages, or comparing OS-reported disk usage to manufacturer specs.

When precision matters — in technical documentation, contracts, or software — always state clearly whether you mean MB (decimal, 10⁶ bytes) or MiB (binary, 2²⁰ bytes).

File Size Converter