Unit Converter
Convert units accurately, with the formula shown.
What is the Unit Converter?
This unit converter handles thirteen categories of measurement — length, weight, area, volume, speed, temperature, pressure, power, energy, torque, voltage, time and digital storage — in one tool instead of scattering them across separate pages. Pick a category, pick your "from" and "to" units, and type a number. Every category except temperature converts by a single exact multiplication factor; temperature also needs an offset, and the tool handles that difference automatically rather than forcing every quantity through the same formula.
It exists for the moment you need a quick, correct conversion and do not want to remember whether a mile is 1609 or 1760 meters. Every factor used is the internationally defined exact value — not a rounded textbook approximation — so chained conversions do not drift.
Why use a free unit converter?
Thirteen quantities, one interface
Length, weight, area, volume, speed, temperature, pressure, power, energy, torque, voltage, time and data all share the same converter, so you learn one interaction pattern and reuse it everywhere.
Exact defined conversion factors
1 inch = 0.0254 m, 1 lb = 0.45359237 kg — the internationally agreed exact values, not rounded decimals that quietly lose precision after a few conversions.
Temperature handled correctly, not forced into a ratio
Every other quantity here is a pure multiplier. Temperature needs a scale and an offset, and the converter applies the right formula for it instead of pretending it behaves like length.
No signup, instant results
Conversion happens in your browser as you type, with no account, no rate limit and no data sent anywhere.
How do you use the Unit Converter?
- 1
Pick a category
Choose length, weight, area, volume, speed, temperature, pressure, power, energy, torque, voltage, time or data storage.
- 2
Choose your units
Select the unit you are converting from and the unit you want it in — for example, feet to meters, or pounds to kilograms.
- 3
Enter your value
Type the number you want converted. The result updates immediately as you type.
How is unit converter calculated?
base = value × toBaseFactor(from) result = base × fromBaseFactor(to)Where:
- base
- The value expressed in the category's base unit — meters for length, kilograms for weight, kelvin for temperature, bits for data, and so on
- toBaseFactor(from)
- The exact multiplier (or, for temperature, function) that converts your source unit into the base unit
- fromBaseFactor(to)
- The exact multiplier (or function) that converts the base unit into your target unit
The simple version
Every quantity has one "home" unit everything else is measured against — meters for length, kilograms for weight, kelvin for temperature. Converting from any unit to any other unit is really two steps: convert your number into the home unit, then convert the home unit into whatever you asked for. This is why the tool can support dozens of unit pairs per category without needing a separate formula for every possible combination — it only needs two conversions per category, one in and one out.
What does it look like in practice?
Length: feet to meters
Input
10 ft
Result
3.048 m
1 ft = 0.3048 m exactly, so 10 × 0.3048 = 3.048.
Weight: pounds to kilograms
Input
150 lb
Result
68.0389 kg
1 lb = 0.45359237 kg exactly (the internationally defined value), so 150 × 0.45359237 = 68.0389 kg.
Speed: km/h to mph
Input
100 km/h
Result
62.14 mph
Both units convert through meters/second: 100 km/h = 27.78 m/s, and 27.78 m/s ÷ (1609.344/3600) = 62.14 mph.
Temperature: Celsius to Fahrenheit
Input
20°C
Result
68°F
The one category that needs an offset as well as a scale factor: 20 × 9/5 + 32 = 68. See the dedicated temperature converter for the full explanation.
How accurate is it?
Every conversion factor used is an internationally defined exact value — 1 inch = 0.0254 m, 1 lb = 0.45359237 kg, 1 GiB = 1,073,741,824 bytes — applied in full double-precision arithmetic. The only rounding happens when the result is formatted for display, not during the calculation itself.
- Common (calendar) units like "month" and "year" in the time category use standard averaged lengths (30.4375 days, 365.25 days) because a month or year has no single fixed length — this is flagged wherever it applies.
- Temperature is calculated with real affine functions (scale and offset), never approximated as a simple ratio.
- Displayed precision scales with the size of the result — very small numbers show more decimal places, very large ones fewer — but the underlying value is never truncated before that final formatting step.
What should you know before using it?
The thirteen categories this converter covers, and their base unit:
| Category | Base unit / notes |
|---|---|
| Length | Meters — mm to nautical miles |
| Weight / mass | Kilograms — mg to UK long tons |
| Area | Square meters — including hectares and acres |
| Volume | Cubic meters — including US and UK (imperial) gallons, cups, tablespoons |
| Speed | Meters/second — km/h, mph, knots, ft/s |
| Temperature | Kelvin — Celsius, Fahrenheit, Kelvin, Rankine (affine, not linear) |
| Pressure | Pascals — bar, atm, psi, torr, mmHg |
| Power | Watts — kW, horsepower (mechanical and metric), BTU/h |
| Energy | Joules — calories, kilocalories, watt-hours, BTU |
| Torque | Newton-meters — pound-feet, pound-inches |
| Voltage | Volts — microvolts to megavolts |
| Time | Seconds — milliseconds to years |
| Digital storage | Bits — decimal (kB/MB/GB) and binary (KiB/MiB/GiB) both supported |
Which tools relate to the unit converter?
The unit converter is one of 14 unit converters on this site. These are the ones most often used alongside it — either because they handle the next step in the same job, or because they answer a question this tool raises.
Length Converter
A focused version of the length category alone, for millimeters through nautical miles.
Weight Converter
A focused version of the weight/mass category, from milligrams to UK long tons.
Temperature Conversion
The one category here that is affine rather than linear — worth its own page because the "why" matters as much as the number.
Byte Converter
A dedicated version of the data-storage category with a decimal/binary toggle, for the kB-vs-KiB question specifically.
Speed Converter
A focused version of the speed category — km/h, mph, knots and ft/s.
When should you use a unit converter?
Because the unit converter runs entirely in your browser, it suits work you would not want to hand to a third-party server — client files, unpublished drafts, anything under an NDA. These are the situations people reach for it in most often.
Cooking and recipes
Convert US volume measurements (cups, tablespoons) to metric, or oven temperatures between Celsius and Fahrenheit.
Open the Cooking and recipesTravel and logistics
Convert distances, speeds and luggage weight limits between metric and imperial systems when crossing borders.
Engineering and DIY
Convert torque specs, pressure ratings or power figures between the units used in a manual and the tools or gauges you actually own.
Fitness and health tracking
Convert body weight and height between kilograms/centimeters and pounds/feet-inches.
Open the Fitness and health trackingFrequently asked questions
How accurate is this unit converter?
Why does temperature convert differently from length or weight?
What is the base unit approach, and why does it matter?
Does this converter handle both US and UK volume units?
Why do I need a separate byte converter if this one already covers data storage?
Are "month" and "year" exact units in the time category?
Is the unit converter safe to use?
This tool runs entirely inside your browser. Your text, files and settings are processed on your own device and are never uploaded to our servers — there is nothing for us to store, log or leak. You can confirm it yourself: open your browser DevTools, switch to the Network tab, and use the tool. You will not see an upload request. It also means the tool keeps working if your connection drops mid-task.
Where do these figures come from?
Every method, threshold and standard this page relies on, with a link to the document that defines it. Check them — a tool that will not show its sources is asking you to take its word for it.
- 1NIST Guide for the Use of the International System of Units (SI)
National Institute of Standards and Technology, SP 811
Supports: The exact conversion factors used across categories, including 1 inch = 0.0254 m and 1 lb = 0.45359237 kg.
- 2The International System of Units (SI Brochure)
Bureau International des Poids et Mesures (BIPM), 9th edition · 2019
Supports: The base-unit approach — meters, kilograms and kelvin as the SI base units every other unit in a category converts through.
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