Unit Converter – Everything You Need to Know

What is a Unit Converter?

A unit converter translates a measurement expressed in one unit into its equivalent in another unit. Converting between metric and imperial, or between two metric prefixes, requires applying a conversion factor — a fixed multiplier that relates the two scales.

For linear unit pairs (like metres and feet), the formula is always:

output = input × factor

For non-linear pairs (temperature scales like Celsius and Kelvin, or Fahrenheit and Celsius), the relationship includes an additive offset:

°F = (°C × 9/5) + 32
K  = °C + 273.15

This tool handles both types automatically.

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The 50 Unit Categories Explained

Everyday Measurements

Category	What it measures	Common example
Length	Distance, size	metres, feet, miles
Mass	Amount of matter	kilograms, pounds, ounces
Volume	Space occupied by a liquid or gas	litres, gallons, fluid ounces
Temperature	Thermal energy	Celsius, Fahrenheit, Kelvin
Speed	Rate of movement	km/h, mph, knots, m/s
Area	Two-dimensional extent	square metres, acres, hectares
Time	Duration	seconds, minutes, hours, days

Scientific and Technical

Category	What it measures
Energy	Work done, heat, electrical energy (joules, BTU, kWh, cal)
Power	Rate of energy transfer (watts, horsepower, BTU/hr)
Pressure	Force per unit area (Pa, psi, bar, atm, mmHg)
Force	Push or pull on an object (newtons, pound-force, kgf)
Torque	Rotational force (N·m, ft·lb, in·lb, kgf·cm)
Frequency	Cycles per second (Hz, kHz, MHz, GHz, rpm)
Angle	Rotation from a reference direction (degrees, radians, gradians)
Density	Mass per volume (kg/m³, g/cm³, lb/ft³)

Digital and Data

Category	What it measures
Digital Storage	File and drive sizes (bits, bytes, KB, MB, GB, TB, PB)
Data Transfer Rate	Network throughput (bps, Kbps, Mbps, Gbps)

Electrical

Category	What it measures
Electric Current	Flow of charge (amperes, milliamperes)
Electric Charge	Total charge (coulombs, milliampere-hours)
Voltage	Electrical potential difference (volts, millivolts, kilovolts)
Capacitance	Ability to store charge (farads, microfarads, picofarads)
Resistance	Opposition to current (ohms, kilohms, megaohms)
Inductance	Opposition to change in current (henries, millihenries)

Thermodynamic and Chemical

Category	What it measures
Fuel Economy	Distance per volume of fuel (mpg, L/100 km, km/L)
Specific Heat	Energy per mass per degree (J/kg·K, BTU/lb·°F)
Dynamic Viscosity	Resistance to flow (Pa·s, poise, centipoise)
Kinematic Viscosity	Viscosity normalised for density (m²/s, stokes)
Illuminance	Light intensity at a surface (lux, foot-candle)

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Metric vs. Imperial: A Quick Reference

The metric system uses a base-10 structure with SI prefixes:

Prefix	Symbol	Multiplier
tera	T	10¹²
giga	G	10⁹
mega	M	10⁶
kilo	k	10³
(base)		1
milli	m	10⁻³
micro	μ	10⁻⁶
nano	n	10⁻⁹
pico	p	10⁻¹²

The imperial system is not base-10. Conversion factors are often non-obvious:

• 1 mile = 5,280 feet = 1,760 yards
• 1 gallon (US) = 4 quarts = 8 pints = 128 fluid ounces
• 1 pound = 16 ounces = 7,000 grains

This is why a converter is useful — there is no pattern to memorise.

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How Conversion Factors Are Calculated

Every unit in this converter is defined by its relationship to an SI base unit. The conversion factor between any two units in the same category is:

factor(A → B) = factor(A → SI) / factor(B → SI)

For example, to convert miles to kilometres:

• 1 mile = 1,609.344 metres (its SI factor)
• 1 kilometre = 1,000 metres (its SI factor)
• 1 mile in kilometres = 1,609.344 / 1,000 = 1.609344 km

All conversions in this tool are computed from authoritative NIST definitions.

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Common Conversion Pairs

Length

• 1 metre = 3.28084 feet
• 1 inch = 2.54 centimetres
• 1 mile = 1.60934 kilometres
• 1 nautical mile = 1,852 metres

Mass

• 1 kilogram = 2.20462 pounds
• 1 pound = 453.592 grams
• 1 stone = 6.35029 kilograms
• 1 metric tonne = 1,000 kilograms

Volume

• 1 litre = 0.264172 US gallons
• 1 US gallon = 3.78541 litres
• 1 fluid ounce (US) = 29.5735 millilitres
• 1 cubic foot = 28.3168 litres

Temperature

• Celsius to Fahrenheit: °F = (°C × 9/5) + 32
• Fahrenheit to Celsius: °C = (°F − 32) × 5/9
• Celsius to Kelvin: K = °C + 273.15
• Rankine to Kelvin: K = R × 5/9

Digital Storage

• 1 kilobyte (KB) = 1,024 bytes (binary) or 1,000 bytes (SI/decimal)
• 1 megabyte (MB) = 1,048,576 bytes (binary)
• 1 gigabyte (GB) = 1,073,741,824 bytes (binary)

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Accuracy and Precision

All conversion factors are stored as IEEE 754 double-precision floating-point numbers (64-bit). This gives roughly 15–17 significant decimal digits of accuracy — more than sufficient for any practical application.

Results are displayed with up to 7 significant figures and switch to scientific notation for values larger than 10¹² or smaller than 10⁻⁶.

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