Data Size Converter Free Online
Convert digital data sizes between bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB), petabytes (PB), and the binary equivalents (KiB, MiB, GiB, TiB). Includes bits as well.
All Conversions
Pro — bulk batch conversion, API access, history & favorites
API access · Priority queue · Team workspace
How It Works
Enter a Size
Type the size value into the From input. Decimals are supported (e.g. 1.5 GB). The conversion runs instantly on every keystroke. Both whole numbers and very small fractions are handled.
Pick Source & Target Units
Choose the source unit (e.g. MB) and the target unit (e.g. MiB). Pay attention to the parenthetical "(1000)" vs "(1024)" — these are not the same! KB (1000 B) is the SI/decimal unit; KiB (1024 B) is the binary IEC unit.
Compare Decimal vs Binary
The All Conversions panel shows your value in every unit at once — both decimal (KB, MB, GB) and binary (KiB, MiB, GiB) side by side. This makes it easy to see why a "1 TB" hard drive shows as ~931 GiB in your operating system: the manufacturer used decimal terabytes, your OS reports binary tebibytes.
Data Size Converter Features
Decimal Units (SI)
The standard SI prefixes used by storage manufacturers, network speeds, and most non-OS contexts: 1 KB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 1 billion bytes, 1 TB = 1 trillion bytes. This is what hard-drive labels, SSD capacities, and Internet speeds use.
Binary Units (IEC)
The IEC binary prefixes used by operating systems and RAM specs: 1 KiB = 1024 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes. RAM is always sold in binary units (4 GiB, 8 GiB, 16 GiB). Windows reports drive sizes in GiB despite labeling them "GB" — the source of much confusion.
Why the Difference Matters
A "1 TB" hard drive is 1,000,000,000,000 bytes (decimal) which equals 0.909 TiB (binary) — that is why your OS shows 931 GiB free, not 1024 GB. RAM uses binary because addressing is binary; storage uses decimal because it is simpler to market (1 TB sounds rounder than 0.909 TiB). Both conventions are correct in their domain.
Live Conversion
The result updates as you type. The All Conversions panel below shows your value in every unit simultaneously — useful for checking whether a 4.7 GB DVD will hold a 4.5 GiB ISO file (it will not — 4.7 GB = 4.376 GiB, less than 4.5 GiB).
Bits Included
A bit is one-eighth of a byte. Network speeds (Mbps, Gbps) are quoted in bits per second, while file sizes are quoted in bytes — that is why a "1000 Mbps" connection downloads at most 125 MB/s (1000/8). The bit unit makes those conversions explicit so you can sanity-check ISP claims.
100% Private
All conversion math runs locally in your browser. No values are transmitted anywhere. Safe for confidential storage planning, capacity projections, or backup sizing.
Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| All 11 units | ||
| Decimal & binary side-by-side | ||
| Live conversion | ||
| Bulk CSV / Excel conversion | — | |
| REST API access | — | |
| Bandwidth & ETA calculator | — |
Frequently Asked Questions
KB (kilobyte, decimal) = 1,000 bytes. KiB (kibibyte, binary) = 1,024 bytes. The IEC introduced the "i" prefixes (KiB, MiB, GiB, TiB) in 1998 to remove ambiguity, because the "kilo/mega/giga" prefixes mean exactly 1000 in physics and engineering but were historically used to mean 1024 in computing. Today storage manufacturers use decimal (KB, MB, GB, TB) while operating systems usually use binary (silently labeled as KB/MB/GB even though the values are KiB/MiB/GiB).
The manufacturer used decimal terabytes: 1 TB = 1,000,000,000,000 bytes. Your operating system displays the same number of bytes but uses the binary tebibyte (often misleadingly labeled as "TB" instead of TiB): 1 TiB = 1,099,511,627,776 bytes. So 1,000,000,000,000 ÷ 1,099,511,627,776 ≈ 0.909 TiB ≈ 931 GiB. The drive is not defective and you have not lost capacity — it is a units mismatch.
Network speeds are traditionally measured in bits per second (Mbps = megabits/sec) because that is the rate at which bits are physically transmitted on the wire. File sizes are in bytes because storage is byte-addressable. To convert: divide Mbps by 8 to get MB/s. So a 1000 Mbps fibre line maxes out at 125 MB/s — meaning a 5 GB game download takes about 40 seconds at line speed.
For technical writing about file sizes, RAM, or anything where the binary value matters, use the IEC units (KiB, MiB, GiB) for clarity. For general writing, "KB" is widely understood — usually meaning whichever value the source software/manufacturer used. Storage marketing always uses decimal. Most OS file managers report binary but label as "KB" — be aware of the ambiguity.
PB (petabyte = 1,000,000,000,000,000 bytes = 1 quadrillion bytes) is included. Beyond PB are exabyte (EB, 1000 PB) and zettabyte (ZB, 1000 EB) — these are useful only for global-scale figures (the entire Internet stores a few hundred zettabytes). We may add them on request.