Unit Converter
Convert length, mass, volume, area, temperature, and more between metric and imperial units.
Unit Converter
Single Conversion
Bulk Unit Conversions
Conversion Statistics
Comprehensive unit conversion!
Convert between metric, imperial, and scientific units with high precision calculations
Measurement systems
Conversion multiplies (or offsets) a value so the physical quantity stays the same while the unit label changes. Metric (SI) scales by powers of 10. Imperial and US customary units use historical ratios. Temperature needs an offset as well as a scale factor.
- SI: meter, kilogram, second, kelvin, and derived units
- US customary / imperial: inch, foot, mile, pound, gallon
- Keep significant figures that match your measurement
- Watch US vs imperial volume (gallon sizes differ)
Handy reference factors
Length
- 1 in = 2.54 cm (exact)
- 1 ft = 0.3048 m
- 1 mi = 1.609344 km
- 1 m ≈ 3.281 ft
Mass
- 1 lb ≈ 0.4536 kg
- 1 oz ≈ 28.35 g
- 1 kg ≈ 2.205 lb
- Troy ounce ≠ avoirdupois ounce
Temperature
- °F = (°C × 9/5) + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15
Dimensional check
Example: 50 mi/h → m/s: 50 × (1609.34 m/mi) × (1 h/3600 s) ≈ 22.35 m/s. Cancel units in the fractions so only the target unit remains.
Common mistakes
- Treating temperature like a pure ratio (forgetting the ±32 or +273.15)
- Mixing US liquid gallon with imperial gallon
- Rounding mid-calculation instead of at the end
- Confusing mass (kg) with weight/force (lbf) in physics contexts
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