Storage Converter — Free MB, GB, TB Calculator

A storage converter for bytes, KB, MB, GB, TB and PB — in both decimal (1000-based) and binary (1024-based, KiB/MiB/GiB) units. Find out why your 1 TB drive shows 931 GB. Free, no sign-up.




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Quick answer: a storage converter translates between decimal units (KB, MB, GB, TB — powers of 1,000, how drives are sold) and binary units (KiB, MiB, GiB, TiB — powers of 1,024, how operating systems measure). Your 1 TB drive shows 931 GB in Windows because 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB — nothing is missing. Convert any pair instantly with the tool above.

How to Use the Storage Converter

  1. Type the value — e.g. 1, 500, 2.5.
  2. Choose From and To units — mix decimal (GB) and binary (GiB) freely; the ⇆ button swaps them.
  3. The result appears instantly, with the exact conversion factor shown underneath.

Why Does My 1 TB Hard Drive Show Only 931 GB?

Nothing is missing. Your drive holds exactly 1,000,000,000,000 bytes — a decimal terabyte. Windows measures capacity in binary gibibytes (GiB) but still labels them “GB”, so it divides 1,000,000,000,000 by 1,073,741,824 and reports 931.3 GiB. The bytes are all there; only the ruler changed.

The 931 GB math: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB — what Windows shows for a 1 TB drive.
Advertised size Actual bytes Windows shows* macOS shows*
64 GB 64,000,000,000 59.6 64 GB
128 GB 128,000,000,000 119 128 GB
256 GB 256,000,000,000 238 256 GB
512 GB 512,000,000,000 477 512 GB
1 TB 1,000,000,000,000 931 1 TB
2 TB 2,000,000,000,000 1,863 2 TB

*Windows counts in binary but labels the result “GB”; macOS has counted in decimal since OS X 10.6 (2009), so it matches the number on the box.

Two more reasons a drive shows even less than 931 GB: formatting overhead — the file system (NTFS, APFS, exFAT) needs a small slice of space for its own bookkeeping — and hidden recovery or system partitions set aside by the manufacturer or the operating system. Together these usually account for a few extra gigabytes, not hundreds.

Decimal vs Binary: KB, MB, GB — and KiB, MiB, GiB

Decimal units (KB, MB, GB) are powers of 1,000; binary units (KiB, MiB, GiB) are powers of 1,024. Computers count in 1,024s because memory is addressed in powers of two (2¹⁰ = 1,024). To end decades of confusion, the IEC introduced the kibi/mebi/gibi/tebi prefixes in 1998 — but the old KB/MB/GB labels stuck on screen, so both systems still share the same names in Windows.

Level Decimal Binary Difference
KB / KiB 1,000 1,024 2.40%
MB / MiB 1,000,000 1,048,576 4.86%
GB / GiB 1,000,000,000 1,073,741,824 7.37%
TB / TiB 1,000,000,000,000 1,099,511,627,776 9.95%

The gap compounds at every level — that is why the discrepancy feels tiny on a 64 GB phone (59.6 GiB) and huge on a 2 TB drive (1,863 GiB).

Who uses which system?

Who Counts in What it means for you
Drive makers (Seagate, WD, Samsung) Decimal A $60 “1 TB” drive = 1,000 GB on the box
Windows Binary, mislabeled “GB” The same drive reads as 931 “GB”
macOS (10.6 and later) Decimal A 1 TB drive reads as 1 TB
iPhone / iPad (iOS 11 and later) Decimal A 128 GB phone reads as 128 GB
Linux Proper IEC labels Shows 931 GiB — honest units
RAM Always binary “16 GB” = 16 GiB = 17.18 decimal GB
Cloud storage billing (e.g. AWS S3) Decimal GB You are billed per 1,000,000,000 bytes
Internet providers Decimal megabits 100 Mbps = 100,000,000 bits per second

Bits vs Bytes: Why Your 100 Mbps Internet Downloads at 12.5 MB/s

Bytes measure storage; bits measure transfer — and 1 byte = 8 bits. Internet providers sell speeds in megabits per second (Mbps), while your browser shows megabytes per second (MB/s). Divide by 8 to compare: 100 Mbps ÷ 8 = 12.5 MB/s maximum, before network overhead. They are not short-changing you; they are quoting a different unit.

A gigabyte in bits: 1 GB = 1,000,000,000 × 8 = 8,000,000,000 bits; 1 GiB = 8,589,934,592 bits.

Planning a big game or 4K download? Run the real numbers on our Bandwidth Calculator — file size plus speed gives you the exact download time.

Data Storage Conversion Table: Bit to Petabyte

Every unit this converter handles, with exact byte values. Decimal (SI) units step by 1,000; binary (IEC) units step by 1,024.

Unit Symbol Exact bytes System
Bit bit 1⁄8 Sub-unit
Byte B 1 Base unit
Kilobyte KB 1,000 Decimal (SI)
Kibibyte KiB 1,024 Binary (IEC)
Megabyte MB 1,000,000 Decimal (SI)
Mebibyte MiB 1,048,576 Binary (IEC)
Gigabyte GB 1,000,000,000 Decimal (SI)
Gibibyte GiB 1,073,741,824 Binary (IEC)
Terabyte TB 1,000,000,000,000 Decimal (SI)
Tebibyte TiB 1,099,511,627,776 Binary (IEC)
Petabyte PB 1,000,000,000,000,000 Decimal (SI)
Pebibyte PiB 1,125,899,906,842,624 Binary (IEC)

Storage Conversion Formulas

Decimal: GB = TB × 1,000 — multiply by 1,000 going down each step, divide going up.
Binary: GiB = TiB × 1,024 — multiply by 1,024 going down each step, divide going up.
Cross-system: GiB = GB ÷ 1.073741824 and GB = GiB × 1.073741824.
Bits ↔ bytes: bits = bytes × 8; bytes = bits ÷ 8.

Worked Examples

2 TB drive → Windows: 2,000,000,000,000 ÷ 1,073,741,824 = 1,862.65 GiB — a 2 TB drive reads as about 1,863 “GB” in Windows.
500 GB SSD → GiB: 500,000,000,000 ÷ 1,073,741,824 = 465.66 GiB of binary-usable space.
1 TiB → GB: 1,099,511,627,776 ÷ 1,000,000,000 = 1,099.51 GB — cross-system conversion the other way.
1 GB → bits: 1,000,000,000 × 8 = 8,000,000,000 bits.

Storage Converter FAQs

Why does my 1 TB hard drive show only 931 GB?
No storage is missing. Manufacturers sell decimal terabytes (1 TB = 1,000,000,000,000 bytes), but Windows measures in binary gibibytes and labels them “GB”: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB. You received every byte you paid for — only the unit changed.
Is 1 TB 1,000 GB or 1,024 GB?
Both — it depends on the unit. 1 TB (terabyte) = 1,000 GB by the decimal SI definition that drive makers use. 1 TiB (tebibyte) = 1,024 GiB by the binary IEC definition that operating systems use. Check whether the “i” is in the symbol.
What is the difference between GB and GiB?
A gigabyte (GB) is 1,000,000,000 bytes — decimal, SI. A gibibyte (GiB) is 1,073,741,824 bytes — binary, IEC — about 7.37% larger. Drive boxes advertise GB; Windows effectively reports GiB.
What is the difference between TB and TiB?
A terabyte (TB) is 1,000,000,000,000 bytes — decimal. A tebibyte (TiB) is 1,099,511,627,776 bytes — binary — about 9.95% larger. 1 TiB equals 1,099.51 GB, which is why a “1 TB” drive shows up as 931 GiB in Windows.
Why is my 500 GB SSD showing 465 GB in Windows?
The same decimal/binary split: 500,000,000,000 bytes ÷ 1,073,741,824 = 465.66 GiB, which Windows labels “GB”. A small extra slice goes to formatting and hidden system partitions.
Does formatting a drive reduce its capacity?
Slightly. The file system (NTFS, APFS, exFAT) needs space for its own bookkeeping — typically well under 1% of a modern drive. The much bigger “loss” is the decimal-vs-binary unit difference, which formatting does not change.
Why does the same drive show 1 TB on a Mac but 931 GB on Windows?
macOS has counted in decimal units since OS X 10.6 (2009), so 1,000,000,000,000 bytes reads as 1 TB. Windows counts in binary units but labels them “GB”, so the same bytes read as 931.3 GiB. Neither is wrong — they use different rulers.
How many bits are in a gigabyte?
8,000,000,000 bits in a decimal gigabyte (1,000,000,000 bytes × 8). A binary gibibyte holds 8,589,934,592 bits. Internet speeds are sold in bits (Mbps), so divide by 8 to estimate download speed in MB/s.
Is 1 GB 1,000 MB or 1,024 MB?
1 GB = 1,000 MB — decimal, how storage is sold and billed. 1 GiB = 1,024 MiB — binary, how Windows measures. For RAM, which is always binary, “1 GB” really means 1 GiB.
What do KiB, MiB, and GiB mean, and when were they introduced?
They are the binary (IEC) units: kibibyte = 1,024 bytes, mebibyte = 1,048,576 bytes, gibibyte = 1,073,741,824 bytes. The IEC introduced them in 1998 to end the confusion with decimal KB, MB, and GB. Linux labels them correctly; Windows uses binary math but keeps the old KB/MB/GB labels.
Are RAM sizes like “16 GB” decimal or binary?
Binary. Memory chips are built in powers of two, so a “16 GB” RAM stick is really 16 GiB = 17,179,869,184 bytes (about 17.18 decimal GB).
How many MB are in a GB for downloads vs what Windows shows?
In billing and on paper, 1 GB = 1,000 MB. In Windows Explorer, what it calls “1 GB” is really 1 GiB = 1,024 MiB — so a 1,000 MB download shows as about 953.7 MiB.