Unit Converter — Length, Weight, Temperature, Area & Speed
Convert units across five categories — length, weight, temperature, area, and speed — all at once. Enter a single value and see it instantly converted to every major metric and imperial unit. Everything runs in your browser; nothing is ever sent anywhere.
Your input is processed entirely in your browser and is never sent anywhere.
Converted values
How to use
- Choose a category: Length, Weight, Temperature, Area, or Speed.
- Type a number into "Value" and pick which unit it's in under "Unit".
- Every other unit in that category updates instantly below — no button needed.
How it works
How the conversion works
For length, weight, area, and speed, each unit has a conversion factor to a base unit for that category (meter for length, kilogram for weight, square meter for area, meters per second for speed). The conversion follows:
value in base unit = input value × input unit's factor
value in output unit = value in base unit ÷ output unit's factor
Temperature is handled differently, using the standard SI formulas for thermodynamic temperature rather than a linear factor:
- Celsius → Fahrenheit:
F = C × 9/5 + 32 - Fahrenheit → Celsius:
C = (F − 32) × 5/9 - Celsius → Kelvin:
K = C + 273.15
Where the conversion factors come from
The factors for length, weight, area, and speed are the exact values defined by international agreement, as published in NIST's "Guide to the SI, Appendix B" (for example, 1 inch = 0.0254 meters exactly, 1 pound = 0.45359237 kilograms exactly). Nautical miles (and knots) use the International Hydrographic Organization's (IHO) definition of the international nautical mile (1 nautical mile = 1,852 meters exactly).
Supported categories and units
- Length: millimeter, centimeter, meter, kilometer, inch, foot, yard, mile, nautical mile
- Weight: milligram, gram, kilogram, metric ton, ounce, pound
- Temperature: Celsius, Fahrenheit, Kelvin
- Area: square millimeter, square centimeter, square meter, square kilometer, are, hectare, acre, square foot
- Speed: meters per second, kilometers per hour, miles per hour, knot, feet per second
Units outside this list (such as traditional regional units or light-years) aren't supported in this version.
FAQ
Is my input sent to a server?
No. All conversion happens entirely inside your browser, and nothing is transmitted to a server.
How accurate are the conversion factors?
Length, weight, area, and speed use the exact values published by NIST (the U.S. National Institute of Standards and Technology) under international agreement. Temperature uses the standard SI formulas. Both are accurate enough for everyday, academic, and professional use.
Does it support traditional regional units or light-years?
This version covers the most commonly used units within length, weight, temperature, area, and speed. Niche units like traditional regional measurements or light-years aren't currently supported.
Can I enter decimal values?
Yes. You can enter numbers with decimal places, and the converted results are shown with decimals as well.
Can I enter negative numbers?
Yes — this is especially useful for the temperature category, where sub-zero Celsius or Fahrenheit values convert correctly.
Related tools
- Base64 Converter — Encode & Decode TextEncode text to Base64, or decode Base64 back to text — with correct handling of emoji and other multi-byte UTF-8 characters. Supports the URL-safe variant for JWTs and URL parameters. Everything runs in your browser; nothing is ever sent anywhere.
- CSV Column EditorExtract, reorder and merge CSV columns. Combine "First name" and "Last name" into a single "Full name" column, or reshape a contact list before importing it elsewhere. Everything runs in your browser — your data is never sent anywhere.
- CSV ⇔ JSON ConverterConvert between CSV and JSON in either direction. Use dot notation in column headers (like user.name) to represent nested objects and arrays. Everything runs in your browser — your data is never sent anywhere.
- JWT Decoder | View Header & Payload in Your Browser (No Signature Verification)Paste a JWT (JSON Web Token) to instantly decode and view its header and payload. This tool does not verify signatures. Everything runs in your browser only — your token is never sent anywhere.
- All tools