Free Online Unit Converters: Length, Weight, Area, Volume, Temperature & Speed in One Place
Convert length, weight, area, volume, temperature and speed across metric, imperial and Chinese units. Type once, see every unit at once — free and private.
Length
From millimeters to kilometers, inches to nautical miles and chi to meters — type once and see every length unit at once.
Weight
From milligrams to tonnes, pounds to carats and jin to liang, one input shows every weight equivalent instantly.
Area
From square millimeters to square kilometers, mu to acres and square feet to square miles — enter once, see every area unit.
Volume
US vs UK gallons clearly separated. From milliliters to cubic meters, fluid ounces to cups, one input shows all volume units.
Temperature
Convert Celsius and Fahrenheit instantly with Kelvin, Réaumur and Rankine shown alongside — no simple-multiplier errors.
Speed
From meters per second to light speed, km/h to mph and knots to Mach — one input shows every speed unit simultaneously.
All units at once
Type one number and see every supported length, weight, area, volume, temperature or speed unit instantly.
Exact international factors
Conversion factors follow the 1959 international yard and pound agreement and SI standards — no approximation errors.
Private and offline-ready
Numbers never leave your browser. The converters work even after you disconnect from the internet.
FinCompute’s free online unit converter hub covers the six quantities that come up most often — length, weight, area, volume, temperature and speed — across metric, imperial and Chinese traditional units. A single input answers every conversion question: inches to cm, pounds to kg, mu to square meters, gallons to liters, Fahrenheit to Celsius, knots to km/h and more.
Metric, imperial and Chinese units in one converter
Where it matters, the converters go beyond metric vs imperial and include traditional Chinese units: li, chi and cun for length; jin, liang, qian and dan for weight; mu for area. This makes the tools genuinely useful for users who switch between international and Chinese-language contexts.
One input, every unit — inches/cm, pounds/kg, mu/m², gallons/liters
Instead of picking a source and target unit from two dropdowns, just type any value into any field. Every other field updates instantly. The result of each row can be copied to the clipboard with one click, and a swap button flips between two units quickly.
Exact international factors: 1959 Yard & Pound Agreement and real offset formulas
Every conversion factor is derived from the International Yard and Pound Agreement of 1959 and the SI standard maintained by BIPM. Temperature uses real offset formulas (not simple multipliers) with Kelvin as the internal base; volume clearly separates US and UK gallons, which differ by about 20%.
Online unit converter runs locally, ms response, works offline
All conversions run in JavaScript inside your browser, with results updating on every keystroke. No value is sent to a server, and no history is stored for conversion inputs. The interface is fully responsive and works the same on phones, tablets and desktops.
FAQ
QWhich unit systems are supported?
Metric (SI), imperial/US customary and, where relevant, Chinese traditional units (li, chi, cun, jin, liang, qian, dan, mu). The volume converter also distinguishes US from UK gallons.
QAre the conversion factors exact?
Yes. Factors for length, weight and area are derived from the international definitions adopted in 1959; temperature uses real offset formulas with Kelvin as the base; speed factors for knots and light speed are exact defined constants.
QCan I copy a specific result?
Yes. Each result row has a copy button that copies an “X unit = Y unit” string to the clipboard for easy pasting into documents, emails or chats.
QWhy are US and UK gallons separate?
1 US gallon ≈ 3.785 L while 1 UK (imperial) gallon ≈ 4.546 L — about 20% different. Mixing them up is a common source of error in cooking, fuel-economy and shipping calculations, so the converter distinguishes them clearly.
QDo the converters work offline?
After the page has finished loading once, yes. All math runs in the browser; no further network requests are needed.