Unit Converter
Convert between 130+ units across 16 categories — length, mass, temperature, speed, data size, and more.
Use on any page (bookmarklet)
Want Unit Converter without leaving the page you're on? Drag the button below to your bookmarks bar, then click it on any website to open Unit Converter right there — it runs entirely in your browser.
Use responsibly: a bookmarklet runs on whatever page you click it on. Avoid sensitive sites such as online banking, payment, or healthcare pages — you run it at your own risk. Everything is processed locally and no data is sent anywhere. See our Terms.
- Show your bookmarks bar if it's hidden — Ctrl+Shift+B (⌘+Shift+B on Mac).
- Drag the button above onto the bookmarks bar.
- Open any website and click the bookmark — the Unit Converter panel appears in the top-right corner. Use ✛ to move it between corners, or ›/‹ to tuck it against the edge and pull it back out.
- Click the bookmark again (or the ✕) to close it.
Note: a few sites with strict security policies may block bookmarklets.
Examples
Length
Input
1 kilometer
Output
1,000 m · 0.621371 mi · 3,280.84 ft
Temperature
Input
100 °C
Output
212 °F · 373.15 K
Data Size
Input
1 GB
Output
1,000,000,000 B · 0.931323 GiB · 8,000 Mb
Speed
Input
100 km/h
Output
27.7778 m/s · 62.1371 mph · 53.9957 kn
Fuel Economy
Input
15 km/L
Output
6.667 L/100km · 35.28 mpg (US)
Pressure
Input
1 atm
Output
101,325 Pa · 1.01325 bar · 14.6959 psi
About this tool
This free unit converter handles 16 measurement categories and 130+ units — all in one place, all in your browser. No upload, no server, no sign-up. Type a value in any unit row and every other unit updates instantly.
Supported categories
- Length — km, m, cm, mm, μm, nm, mi, yd, ft, in, nmi, light year
- Mass — metric ton, kg, g, mg, μg, lb, oz, stone, short/long ton, carat
- Area — km², m², cm², ha, ac, mi², yd², ft², in², pyeong (평)
- Volume — m³, L, mL, cm³, in³, ft³, US/Imperial gal·qt·pt·cup·fl oz
- Speed — m/s, km/h, mph, knot, ft/s, Mach, speed of light
- Time — ns, μs, ms, s, min, h, d, wk, mo, yr, decade, century
- Temperature — °C, °F, K, °R (with offset-aware formulas)
- Pressure — Pa, kPa, MPa, bar, mbar, atm, mmHg, psi, ksi
- Energy — J, kJ, MJ, cal, kcal, Wh, kWh, eV, BTU, ft·lb, erg
- Fuel Economy — km/L, L/100km, mpg (US & UK), mi/L
- Frequency — Hz, kHz, MHz, GHz, THz, RPM, rad/s
- Plane Angle — °, rad, grad, arcminute, arcsecond, turn, mrad
- Data Size — bit, B, KB/MB/GB/TB/PB (SI) and KiB/MiB/GiB/TiB (IEC)
- Data Rate — bps, Kbps, Mbps, Gbps, Tbps, B/s, KB/s, MB/s, GB/s
- Power — W, kW, MW, GW, hp (mech & metric), BTU/h, kcal/h
- Force — N, kN, MN, kgf, lbf, ozf, dyne, ton-force
Conversion formulas
Every row shows its exact formula relative to the base unit, so you can see exactly how each conversion works — useful for homework, engineering checks, or just satisfying curiosity. Special cases like temperature (offset-based) and fuel economy (reciprocal L/100km) are handled with their correct, non-linear formulas rather than simple multiplication.
Privacy
Everything runs client-side in your browser. No values you enter are ever sent to a server.
Frequently asked questions
How do I convert a unit?
Select a category (Length, Mass, Temperature, etc.), then type a value in any unit row. All other units update instantly. Click a different row to convert from that unit instead.
Is this unit converter free?
Yes — completely free, no sign-up required. All conversions run in your browser with no data sent to any server.
How is temperature converted between Celsius, Fahrenheit, and Kelvin?
Fahrenheit = Celsius × 9/5 + 32. Kelvin = Celsius + 273.15. To go the other way: Celsius = (Fahrenheit − 32) × 5/9, and Celsius = Kelvin − 273.15.
What is the difference between KB and KiB?
KB (Kilobyte) = 1,000 bytes — the SI standard used by storage manufacturers. KiB (Kibibyte) = 1,024 bytes — the IEC binary standard used by operating systems. The same gap applies to MB vs MiB, GB vs GiB, and so on.
What is L/100km and how does it relate to km/L?
L/100km measures how many litres it takes to travel 100 kilometres — lower is more efficient. km/L measures how many kilometres you travel per litre — higher is better. They are reciprocals: km/L = 100 ÷ L/100km.
What categories are supported?
Length, Data Rate, Data Size, Area, Volume, Speed, Time, Pressure, Energy, Fuel Economy, Temperature, Frequency, Mass, Plane Angle, Power, and Force — 16 categories with 130+ units total.
How is Mach speed calculated?
Mach 1 equals the speed of sound at sea level (approximately 340.29 m/s or 1,225 km/h at 15 °C and 101.325 kPa). This value varies with altitude and temperature; the converter uses the standard sea-level value.
What is a Pyeong (평)?
Pyeong is a traditional Korean unit of area equal to 400/121 ≈ 3.3058 square metres, or roughly 35.58 square feet. It is commonly used in Korean real estate to measure floor area.
Learn more
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