Data size converter
Bytes, KB, MB, GB… and KiB, MiB and GiB too. Both systems side by side, which is the only way to see why your 1 TB drive shows 931 GB.
Your figures
Result
- Bits
- 8,000,000,000
- kB
- 1,000,000.00
- MB
- 1,000.00
- GB
- 1.000
- TB
- 0.0010
- KiB
- 976,562.50
- MiB
- 953.67
- GiB
- 0.931
- TiB
- 0.0009
- Download at 100 Mbps (s)
- 80.0
What we assume
- Converted in your browser.
- kB, MB, GB and TB are decimal (powers of 1000), as SI defines them and as drive manufacturers sell them.
- KiB, MiB, GiB and TiB are binary (powers of 1024), as your operating system counts them. Both are correct; mixing them is not.
- A byte is 8 bits. Network speeds are quoted in bits and file sizes in bytes, another classic source of confusion.
- The download time is theoretical: a clean 100 Mbps, no protocol overhead and no loss. In practice add 10% to 20%.
How it is calculated
A byte is eight bits. From there, there are two ways of counting, and both genuinely exist — which explains nearly every misunderstanding about the size of things.
Why your 1 TB drive shows 931 GB
The manufacturer counts in powers of 1000: 1 TB is a trillion bytes. The operating system counts in powers of 1024 and calls «GB» what is strictly a GiB. A trillion bytes is 931.32 GiB, so the drive has not shrunk and nobody lied: two different units with similar names are being used.
Bits and bytes in the same sentence
Your connection is advertised in megabits per second and your files are measured in megabytes. Since a byte is eight bits, a 100 Mbps line downloads at most 12.5 MB per second. That division by eight is the one people forget when working out how long something takes.
An example
1 GB is 1,000,000,000 bytes, which is 0.931 GiB. At 100 Mbps it takes 80 seconds to download, at best.
Frequently asked questions
What is the difference between GB and GiB?
A GB is 1,000,000,000 bytes and a GiB is 1,073,741,824. The gap is 7.4% and grows with each step: at TB it is already 10%.
Why does Windows say «GB» when it means GiB?
History. Before KiB/MiB/GiB notation existed, «KB» meant 1024 bytes in computing. The binary prefixes arrived in 1998 and Windows never changed the labels. macOS and Linux did.
How long does a download really take?
Longer than the figure here. This is the theoretical ceiling: it ignores TCP overhead, latency and the fact that advertised speeds are rarely reached. Add 10% to 20%.
What about RAM?
It is always sold and measured in powers of 1024, so an «8 GB» module really is 8 GiB. There, oddly enough, there is no discrepancy.
Keep calculating
All tools →- Number base converter Binary, octal, decimal and hex, both ways. With genuinely large integers: 64-bit values come out exact.
- Unix timestamp converter Timestamp to date and date to timestamp. If the number is in milliseconds we spot it, which is the mistake that wastes the most time.
- HEX, RGB and HSL colour converter Hexadecimal, RGB and HSL, all three ways. Plus the contrast, which is what decides whether readable text fits on top.
- Character, word and byte counter Characters, words, lines and bytes. Counted properly: an emoji is one character, whatever your editor says.
Updated on 2026-09-02. Calculations run in your browser; nothing you type is sent to a server.