Why does my hard drive show less space than advertised?

Hard drive manufacturers use decimal units (1 GB = 1,000,000,000 bytes), while operating systems use binary units (1 GiB = 1,073,741,824 bytes). A 500 GB drive shows as about 465 GiB in Windows because of this difference.

What is the difference between GB and GiB?

GB (gigabyte) uses decimal: 1 GB = 1,000,000,000 bytes. GiB (gibibyte) uses binary: 1 GiB = 1,073,741,824 bytes (1024³). The binary units (KiB, MiB, GiB) were standardized by IEC to reduce confusion.

How many MB are in a GB?

In decimal (SI): 1 GB = 1,000 MB. In binary (IEC): 1 GiB = 1,024 MiB. Most software uses binary internally but displays decimal labels, causing confusion.

A petabyte (PB) is 1,000 terabytes in decimal or 1,024 tebibytes in binary. That's approximately 1 quadrillion bytes—enough to store about 500 billion pages of text.

Which units should I use for file sizes?

For accuracy, use binary units (KiB, MiB, GiB) when discussing RAM and file sizes in operating systems. Use decimal units (KB, MB, GB) when discussing storage capacity as marketed by manufacturers.

Data Storage Converter Online 2026 | GB, MB, TB, KB

What is a Data Storage Converter?

A data storage converter transforms digital storage measurements between different units. Data storage is measured in bytes (and multiples thereof), but there are two competing standards: binary (base-1024) used by operating systems and decimal (base-1000) used by storage manufacturers.

This converter supports both standards, helping you understand why your "500 GB" hard drive shows only 465 GB in Windows, and enabling accurate calculations for file sizes, bandwidth, and storage capacity.

Binary vs Decimal: Why the Confusion?

The confusion arose because computers use binary (powers of 2), but the metric prefixes (kilo, mega, giga) traditionally mean powers of 1000:

Binary (IEC standard): 1 KiB = 1,024 bytes (2¹⁰). Used by operating systems, RAM, and file sizes.
Decimal (SI standard): 1 kB = 1,000 bytes (10³). Used by storage manufacturers and network speeds.

The IEC introduced new prefixes (kibi, mebi, gibi) in 1998 to eliminate ambiguity, but adoption has been slow.

Conversion Formulas

Binary Units (IEC) - Factor of 1024:
1 KiB (Kibibyte) = 1,024 Bytes
1 MiB (Mebibyte) = 1,024 KiB = 1,048,576 Bytes
1 GiB (Gibibyte) = 1,024 MiB = 1,073,741,824 Bytes
1 TiB (Tebibyte) = 1,024 GiB = 1,099,511,627,776 Bytes
1 PiB (Pebibyte) = 1,024 TiB

Decimal Units (SI) - Factor of 1000:
1 kB (Kilobyte) = 1,000 Bytes
1 MB (Megabyte) = 1,000 kB = 1,000,000 Bytes
1 GB (Gigabyte) = 1,000 MB = 1,000,000,000 Bytes
1 TB (Terabyte) = 1,000 GB = 1,000,000,000,000 Bytes
1 PB (Petabyte) = 1,000 TB

Bits to Bytes:
1 Byte = 8 bits

Why Hard Drives Show Less Space

When you buy a "1 TB" hard drive, the manufacturer means 1,000,000,000,000 bytes (decimal TB). But Windows displays sizes using binary units:

1 TB (decimal) = 1,000,000,000,000 bytes
In binary: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB

So your "1 TB" drive shows as ~931 GB in Windows!

This isn't missing space—it's a unit conversion difference. Add system files and formatting overhead, and you'll see even less usable space.

Common Storage Conversions

GiB to GB: Multiply by 1.074 (1 GiB = 1.074 GB)
GB to GiB: Multiply by 0.931 (1 GB = 0.931 GiB)
MiB to MB: Multiply by 1.049 (1 MiB = 1.049 MB)
TiB to TB: Multiply by 1.1 (1 TiB = 1.1 TB)
Bytes to bits: Multiply by 8

Benefits of Using This Converter

Clarity between standards: Understand binary vs decimal units and why sizes differ.
Accurate calculations: Plan storage needs and verify actual vs advertised capacity.
Bandwidth planning: Convert between bits and bytes for network calculations.
Comprehensive units: Supports bytes, bits, and all common prefixes.
Quick reference: Shows byte-level breakdown for each conversion.

When to Use Which Standard

Use Binary (KiB, MiB, GiB):

Discussing RAM capacity (always binary)
File sizes shown in operating systems
Programming and memory allocation

Use Decimal (kB, MB, GB):

Storage device marketing and specifications
Network bandwidth (Mbps is always decimal)
Scientific and telecommunications contexts

Frequently Asked Questions

Why does my 256 GB SSD show only 238 GB?

256 GB (decimal) = 256,000,000,000 bytes. In binary: 256,000,000,000 ÷ 1,073,741,824 = 238.42 GiB. Windows displays GiB but labels it "GB," causing the apparent discrepancy.

Is RAM measured in GB or GiB?

RAM is always measured in binary units. When you have "16 GB" of RAM, you actually have 16 GiB (17,179,869,184 bytes). RAM manufacturers use "GB" colloquially but mean GiB.

What's the difference between Mbps and MBps?

Mbps (megabits per second) measures network speed. MBps (megabytes per second) is 8× larger. A 100 Mbps connection downloads at about 12.5 MBps maximum. Network speeds always use decimal megabits.

How much is a petabyte?

1 PB (decimal) = 1,000 TB = 1,000,000 GB. In perspective: 1 PB could store about 500 billion pages of text, 3.4 years of 24/7 HD video, or 13.3 years of continuous MP3 music.

Why did IEC create new unit names?

The IEC introduced kibi, mebi, gibi, etc. in 1998 because using "kilo" for both 1000 and 1024 caused confusion in specifications, contracts, and technical documents where precision matters.

Which is correct: KB or kB?

Technically, "kB" (lowercase k) is the SI symbol for 1000 bytes. "KB" with uppercase K is ambiguous but commonly used for 1024 bytes. For clarity, use "KiB" for 1024 bytes.