Data Storage & Bandwidth Converters

56 converters, all running in your browser.

Two separate ambiguities make data conversion harder than it looks, and both cost people money.

Bits against bytes. A byte is eight bits. Network speeds are quoted in bits per second and file sizes in bytes, so a 100 Mbps connection downloads at roughly 12.5 MB/s, not 100. The capital B is the only thing distinguishing them — MB is megabytes, Mb is megabits — and it is the single most common misreading in the field.

1000 against 1024. Storage manufacturers use decimal prefixes, where a terabyte is 10¹² bytes. Operating systems have historically used binary ones, where what they call a terabyte is 2⁴⁰ bytes. The gap widens with scale: 7% at the gigabyte, 10% at the terabyte — which is why a "1 TB" drive shows as about 931 GB in Windows. Nothing is missing; the two systems are counting differently.

The IEC prefixes (KiB, MiB, GiB) exist to remove the ambiguity and are used consistently by Linux tooling and almost nowhere else. These converters use decimal prefixes throughout.

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Conversion factors

From	To	Multiply by
Bits	Bytes	0.125
Bits	Kilobits	0.001
Bits	Kilobytes	1.2500e-4
Bits	Megabits	1.0000e-6
Bits	Megabytes	1.2500e-7
Bytes	Bits	8
Bytes	Kilobits	0.008
Bytes	Kilobytes	0.001
Bytes	Megabits	8.0000e-6
Bytes	Megabytes	1.0000e-6
Kilobits	Bits	1000
Kilobits	Bytes	125
Kilobits	Kilobytes	0.125
Kilobits	Megabits	0.001
Kilobits	Megabytes	1.2500e-4
Kilobytes	Bits	8000
Kilobytes	Bytes	1000
Kilobytes	Kilobits	8
Kilobytes	Megabits	0.008
Kilobytes	Megabytes	0.001

Working Out a Real Download Time

The arithmetic people want from a data converter is usually "how long will this take", and it has three steps that are each easy to get wrong.

Take a 25 GB file on a 200 Mbps connection:

1. Convert the file to bits. 25 GB × 8 = 200 gigabits. 2. Divide by the line rate. 200 Gb ÷ 200 Mbps = 1,000 seconds. 3. Add overhead. TCP, encryption and protocol framing cost 5–15%, so budget around 18–19 minutes rather than the 16.7 the division gives.

The most common mistake is skipping step one, which makes the answer eight times too optimistic.

Why Your Drive Shows Less Than the Box Says

A drive sold as 1 TB holds 10¹² bytes. Windows reports capacity in binary units while calling them by decimal names, so it shows about 931 "GB". Nothing has been lost and no space is missing — the two systems count differently, and the gap grows with size: about 2.4% at the kilobyte, 7.4% at the gigabyte, 10% at the terabyte.

macOS switched to decimal reporting in 2009, which is why the same drive shows 1 TB there and 931 GB on Windows.

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