Length, weight, temperature, and 12 more measurement categories. Free, private, runs in your browser.
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The unit converter covers the fifteen categories that cover more than 95% of real-world conversions: length, weight, temperature, volume, area, speed, time, pressure, energy, power, digital storage, frequency, voltage, current, and apparent power. Within each, every unit is convertible to every other — feet to metres, kilograms to pounds, Celsius to Fahrenheit, joules to calories. The tool picks sensible defaults per category so you land on a recognisable conversion immediately instead of needing to configure two dropdowns before seeing a number.
Most unit conversions are pure ratios — 1 metre is always 3.28084 feet, regardless of the starting value. Temperature is different because zero on each scale represents a different physical state. Zero Celsius is the freezing point of water; zero Fahrenheit is arbitrary; zero Kelvin is absolute zero. Converting between them requires an offset as well as a scale. This tool handles that math correctly — 0°C returns 32°F (not 0°F), 100°C returns 212°F, and negative temperatures work in both directions. Kelvin and Rankine are included for scientific contexts.
Most of the world uses metric; the US, Liberia, and Myanmar use imperial. Even within imperial, the US uses some slightly different units than the UK (the US gallon is 3.785 litres; the UK Imperial gallon is 4.546 litres — different by almost 20%). Unit dropdowns label the system (metric vs imperial vs US customary) next to each option so you pick the exact variant you want. This matters for cooking, engineering specs, and any cross-border conversion.
Constants behind the conversions are the standard scientific values: exactly 1 inch = 25.4 mm, exactly 1 lb = 0.45359237 kg, exactly 1 ft = 0.3048 m. Results display to about 8 decimal places of precision. For trade-regulated or aerospace-grade work, always cross-reference with your local standards body (NIST, BIPM); for day-to-day use, classroom coursework, and professional-but-not-safety-critical calculations, the precision is more than enough.
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Fifteen: length, weight (mass), temperature, volume, area, speed, time, pressure, energy, power, digital storage, frequency, voltage, current, and apparent power. Every unit within a category is convertible to every other in that category.
Yes. Temperature conversions are offset-aware, so 0°C correctly converts to 32°F (not 0°F). The same applies to Kelvin and Rankine. Other categories use simple ratio math, which is why they're faster but temperature needs special handling.
Accurate to about 8 decimal places. The underlying constants are the standard scientific values (exactly 1 inch = 25.4 mm, 1 lb = 0.45359237 kg, etc.). For regulated engineering work, always cross-reference with your local standards body — but for day-to-day conversions, scientific coursework, or quick engineering estimates, the results are trustworthy.