About this unit converter
This tool converts values across 8 categories: length, weight, temperature, volume, area, speed, time and digital data. All conversions happen locally in your browser using standard reference factors — no values are sent to a server.
Supported units
- Length: mm, cm, m, km, inch, foot, yard, mile
- Weight: mg, g, kg, ton, ounce, pound, stone
- Temperature: Celsius, Fahrenheit, Kelvin
- Volume: mL, cL, dL, L, m³, US/UK fluid ounce, cup, pint, quart, gallon
- Area: mm², cm², m², hectare, km², in², ft², yd², acre, mi²
- Speed: m/s, km/h, mph, ft/s, knots
- Time: ms, s, min, h, day, week, month, year
- Data: bit, byte, KB/KiB, MB/MiB, GB/GiB, TB/TiB
Decimal vs binary data sizes
For digital data, this tool distinguishes decimal (KB = 1000 bytes, used by storage manufacturers) from binary (KiB = 1024 bytes, used by operating systems). This is why a 1 TB hard drive shows as ~931 GiB in your file manager.
Frequently asked questions
Why does a 1 TB hard drive show 931 GB in Windows?
Drive manufacturers measure in TB (10¹²), but Windows displays in GiB (2³⁰ = 1,073,741,824 bytes). Dividing: 1,000,000,000,000 ÷ 1,073,741,824 ≈ 931 GiB. This is neither a bug nor deceptive marketing — it is the absence of consensus between the SI decimal prefix and the binary prefix. The IEC 80000-13 standard introduced kibi/mebi/gibi prefixes to disambiguate, but Windows and most consumer operating systems continue to display binary sizes while labelling them GB.
How many centimetres is exactly 1 inch?
Exactly 2.54 cm, by international definition adopted in 1959 (International Yard and Pound Agreement). This is not an approximation: 1 inch = 25.4 mm absolutely and precisely. The cascade: 1 foot = 30.48 cm exactly, 1 yard = 91.44 cm exactly, 1 statute mile = 1,609.344 m exactly. Before 1959, a tiny divergence existed between the British and American inch — the 1959 agreement resolved it permanently.
What is the difference between kg and newtons when measuring weight?
The kilogram measures mass (the quantity of matter, invariant throughout the universe); the newton measures force, including weight (F = m × g, standard g = 9.80665 m/s²). On Earth, 1 kg weighs ≈ 9.81 N. On the Moon (g ≈ 1.62 m/s²), that same kilogram weighs only 1.62 N — its mass remains 1 kg. When your doctor says you weigh 70 kg, it is a common shorthand: your mass is 70 kg, your weight is technically ~686 N.
Why is the US gallon different from the UK gallon?
Both descend from the medieval English gallon, but diverged in 1824 when Parliament redefined the imperial gallon as the volume of 10 pounds of distilled water (4.546 L). The United States, independent since 1776, had retained the older wine gallon of 231 cubic inches (3.785 L) — a gap of roughly 20%. This propagates to the pint (UK 568 ml, US 473 ml) and fluid ounce (UK 28.4 ml, US 29.6 ml). Always verify which system a recipe, fuel specification, or contract references.
What does the 2019 kilogram redefinition actually change for everyday users?
For daily life, nothing at all — your scale reads the same. The impact is metrological. Before 2019, the kilogram was defined by a platinum-iridium cylinder at Sèvres that had drifted ~50 micrograms over a century. Since 20 May 2019, it is defined by the Planck constant (h = 6.626 070 15 × 10⁻³⁴ J·s), which is universal and invariant. No physical artefact is needed: the definition is reproducible in any suitably equipped laboratory anywhere in the universe. The Sèvres prototype is now a museum piece.
