Why does my hard drive show less space than advertised?

Manufacturers use decimal (1 GB = 1,000,000,000 bytes) while your OS uses binary (1 GiB = 1,073,741,824 bytes). A 1 TB drive has 1,000,000,000,000 bytes, which is 931.3 GiB. The bytes are all there — it is a labeling difference.

What is the difference between MB and MiB?

MB (megabyte) officially means 1,000,000 bytes (decimal), while MiB (mebibyte) means 1,048,576 bytes (binary). In practice, many people and programs use MB to mean the binary value, causing confusion.

How many photos can fit in 1 GB?

Roughly 200-500 photos at typical smartphone quality (2-5 MB each). A 12 MP image (JPEG) is typically 3-5 MB, while RAW files can be 25-50 MB each, fitting only 20-40 in 1 GB.

How big is a petabyte?

A petabyte is 1,024 terabytes (binary) or 1,000 terabytes (decimal). To visualize: it could store about 500 billion pages of text, 3.4 years of 24/7 4K video, or 250,000 DVDs.

Is 1 KB equal to 1,000 or 1,024 bytes?

Both, depending on context. IEC standard (KiB) uses 1,024 bytes (binary). SI standard (KB) uses 1,000 bytes (decimal). Operating systems typically use binary, while storage manufacturers use decimal.

What comes after petabyte?

Exabyte (EB, 10^18), zettabyte (ZB, 10^21), yottabyte (YB, 10^24). In binary: exbibyte (EiB), zebibyte (ZiB), yobibyte (YiB). Global data creation is measured in zettabytes.

Byte Converter

Convert between bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes. Binary (1024) and decimal (1000) standards, visual scale bar, and storage reference.

Value

Unit

Standard

Bytes (B)

1,073,741,824

IEC: B

Kilobytes (KB)

1,048,576

IEC: KiB

Megabytes (MB)

1,024

IEC: MiB

Gigabytes (GB)

1.00

IEC: GiB

Terabytes (TB)

9.766e-4

IEC: TiB

Petabytes (PB)

9.537e-7

IEC: PiB

Size Scale

1.00 GB

0.1%

0.0%

Binary vs. Decimal Standard

Unit	Binary (×1024)	Decimal (×1000)	Difference
KB	1,048,576.0000	1,073,741.8240	+2.40%
MB	1,024.0000	1,073.7418	+4.86%
GB	1.0000	1.0737	+7.37%
TB	9.766e-4	1.074e-3	+9.95%
PB	9.537e-7	1.074e-6	+12.59%

Storage Size Reference

Unit	Binary (IEC)	Bytes	Common Use
KB	KiB	1,024	Small text files, emails
MB	MiB	1,048,576	Photos, MP3 songs (3-5 MB)
GB	GiB	1,073,741,824	HD movies (4-5 GB), apps
TB	TiB	1,099,511,627,776	Hard drives, large databases
PB	PiB	1,125,899,906,842,624	Data centers, cloud storage

Planning notes, formulas, and examples

About the Byte Converter

Digital storage is measured in bytes, but the leap from bytes to kilobytes, megabytes, gigabytes, and beyond causes constant confusion — especially since the computing industry uses two different standards. The binary standard (used by operating systems) defines 1 KB = 1,024 bytes, while the decimal standard (used by hard drive manufacturers) defines 1 KB = 1,000 bytes. This difference compounds at larger scales: a "1 TB" hard drive shows as ~931 GB in your OS.

This converter handles all common units from bytes through petabytes in both standards. Enter a value in any unit and see the equivalent in all others, along with a visual scale bar showing relative size. The binary vs. decimal comparison table shows exactly how much the two standards diverge at each scale — explaining why your new hard drive always seems to have less space than advertised.

Whether you are planning storage purchases, calculating file transfer times, estimating backup sizes, or comparing cloud storage tiers, it gives accurate conversions with the context needed to choose the right standard for your use case.

When This Page Helps

The binary/decimal distinction confuses everyone. This converter shows both standards side-by-side, explains the discrepancy, and includes a visual scale bar. It answers the perpetual question: "Why does my 1 TB drive only show 931 GB?" with practical numbers for buying decisions, planning, support troubleshooting, and documentation clarity in technical teams.

How to Use the Inputs

Enter the storage amount in the Value field.
Select the source unit (Bytes, KB, MB, GB, TB, or PB).
Choose the standard: Binary (1024-based) or Decimal (1000-based).
Read all converted values from the output cards.
Compare binary vs. decimal in the comparison table.
Use presets for common sizes like DVDs, Blu-rays, or RAM modules.

Formula used

Binary standard: 1 KB = 1,024 B, 1 MB = 1,024 KB, 1 GB = 1,024 MB, 1 TB = 1,024 GB, 1 PB = 1,024 TB.
Decimal standard: 1 KB = 1,000 B, 1 MB = 1,000 KB, 1 GB = 1,000 MB, 1 TB = 1,000 GB, 1 PB = 1,000 TB.
Conversion: value_in_bytes = value × factor_of_source_unit; result = value_in_bytes ÷ factor_of_target_unit.

Example Calculation

Result: 1,024 GB (binary) or 1,000 GB (decimal)

1 TB in binary = 1,024 GB = 1,048,576 MB = 1,099,511,627,776 bytes. In decimal, 1 TB = 1,000 GB = 1,000,000,000,000 bytes. The difference is 99.5 billion bytes (~7.4%).

Tips & Best Practices

Hard drive manufacturers use decimal (1000-based), so a "1 TB" drive is ~931 GiB in your OS.
RAM is always measured in binary powers: 4 GB = 4 × 1,073,741,824 bytes exactly.
IEC prefixes (KiB, MiB, GiB) explicitly mean binary. SI prefixes (KB, MB, GB) technically mean decimal.
Network speeds use decimal bits: 100 Mbps = 100,000,000 bits/s = ~12.5 MB/s.
The binary-decimal gap grows with scale: ~2.4% at KB, ~4.9% at MB, ~7.4% at GB, ~10% at TB.
Cloud storage pricing is typically decimal: 1 TB plan = 1,000,000,000,000 bytes.

The Binary vs. Decimal Divide

The confusion dates to the 1960s when computing adopted powers of 2 (since binary hardware naturally works in 1024s). As storage grew, manufacturers started using decimal prefixes for marketing (1,000 sounds bigger than 1,024 hurts). In 1998, the IEC introduced KiB/MiB/GiB to disambiguate, but adoption has been slow. Today, Windows shows binary sizes while macOS switched to decimal in 2009.

Storage Planning

When buying storage, calculate needs in binary for OS compatibility: a 256 GB SSD provides ~238 GiB usable (minus filesystem overhead). For cloud services priced in decimal GB, the numbers match the listed capacity. Always check whether a service quotes binary or decimal when comparing prices per GB.

Data Transfer Estimation

To estimate transfer time: divide file size (in bits) by connection speed (in bits/second). Remember: 1 byte = 8 bits. A 1 GB file over 100 Mbps: 8,589,934,592 bits ÷ 100,000,000 bps ≈ 86 seconds. Account for protocol overhead (typically 5-10% slower than theoretical maximum).

Sources & Methodology

Last updated: March 8, 2026

Frequently Asked Questions

Manufacturers use decimal (1 GB = 1,000,000,000 bytes) while your OS uses binary (1 GiB = 1,073,741,824 bytes). A 1 TB drive has 1,000,000,000,000 bytes, which is 931.3 GiB. The bytes are all there — it is a labeling difference.