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79 converters spanning 720+ units — length, mass, temperature, pressure, energy, electricity, radiology and currency. Results calculate as you type. No account, no paywall, no waiting.
Length Converter
Common conversions
The 34 people look up most — each on its own page, ready to bookmark.
Every converter, by category
Grouped the way engineers, scientists and tradespeople actually look for them.
Common Converters
18 convertersLength
Meters, feet, inches, miles and 20 more
⚖Weight and Mass
Kilograms, pounds, ounces, tons, carats
▢Volume
Liters, gallons, cups, pints, cubic meters
°Temperature
Celsius, Fahrenheit, Kelvin, Rankine
▦Area
Square meters, acres, hectares, square feet
⇲Pressure
Pascals, bar, psi, atmospheres, mmHg
⚡Energy
Joules, calories, kilowatt-hours, BTU
▣Volume - Dry
Dry pints, quarts, pecks and bushels
$Currency
Live exchange rates for 160+ world currencies
AaCase Converter
UPPERCASE, lowercase, Title Case, camelCase, snake_case
◉Power
Watts, horsepower, BTU/hour
⇥Force
Newtons, pound-force, kilogram-force, dynes
◷Time
Seconds, hours, days, years, centuries
→Speed
km/h, mph, knots, meters per second, Mach
∠Angle
Degrees, radians, gradians, arcminutes
⛽Fuel Consumption
MPG, L/100km, km/L — US and UK
10Numbers (Base) Converter
Binary, octal, decimal, hexadecimal, base 2–36
▤Data Storage
Bytes, megabytes, gigabytes, terabytes
Engineering Converters
8 convertersVelocity - Angular
RPM, radians/second, degrees/second
⇗Acceleration
m/s², g-force, ft/s²
↺Acceleration - Angular
Radians and revolutions per second squared
◈Density
kg/m³, g/cm³, lb/ft³
◇Specific Volume
m³/kg, ft³/lb, L/kg
⊙Moment of Inertia
kg·m², lb·ft², g·cm²
⤿Moment of Force
Newton·meter, pound-force·foot
⟳Torque
Newton·meter, lbf·ft, kgf·m
Heat Converters
10 convertersFuel Efficiency - Mass
Energy per unit mass: J/kg, BTU/lb, cal/g
◑Fuel Efficiency - Volume
Energy per unit volume: J/m³, BTU/ft³
ΔTemperature Interval
Temperature differences (no zero offset)
⇔Thermal Expansion
Coefficient of thermal expansion, 1/K
⊗Thermal Resistance
K/W, °F·h/BTU
≋Thermal Conductivity
W/(m·K), BTU/(h·ft·°F)
◍Specific Heat Capacity
J/(kg·K), BTU/(lb·°F), cal/(g·°C)
▩Heat Density
Energy per unit area: J/m², langley
⌁Heat Flux Density
W/m², BTU/(h·ft²)
⊞Heat Transfer Coefficient
W/(m²·K), BTU/(h·ft²·°F)
Fluids Converters
10 convertersFlow
Volumetric flow: m³/s, L/min, GPM, CFM
⇉Flow - Mass
Mass flow: kg/s, lb/h, ton/hour
⋯Flow - Molar
Molar flow: mol/s, kmol/h
⇊Mass Flux Density
kg/(m²·s), lb/(ft²·s)
◎Concentration - Molar
mol/L, mmol/L, molarity
◌Concentration - Solution
kg/L, g/L, mg/L, ppm
◔Viscosity - Dynamic
Pa·s, poise, centipoise
◕Viscosity - Kinematic
m²/s, stokes, centistokes
◠Surface Tension
N/m, dyne/cm, mN/m
⌸Permeability
Water-vapour permeability, perms
Light Converters
5 convertersElectricity Converters
15 convertersCharge
Coulomb, ampere-hour, elementary charge
⊖Linear Charge Density
Coulomb per metre
⊘Surface Charge Density
Coulomb per square metre
⊜Volume Charge Density
Coulomb per cubic metre
⚊Current
Ampere, milliampere, abampere
⚌Linear Current Density
Ampere per metre
⚍Surface Current Density
Ampere per square metre
⇡Electric Field Strength
Volt per metre
⌇Electric Potential
Volt, millivolt, kilovolt
≠Electric Resistance
Ohm, kilohm, megohm
≢Electric Resistivity
Ohm·metre, ohm·centimetre
≡Electric Conductance
Siemens, mho, microsiemens
⋚Electric Conductivity
Siemens per metre, µS/cm
⊣Electrostatic Capacitance
Farad, microfarad, picofarad
⊢Inductance
Henry, millihenry, microhenry
Magnetism Converters
4 convertersRadiology Converters
4 convertersWorth reading
Original writing on where these units came from and where conversion goes wrong.
Metric vs Imperial: Why the United States Never Switched
The US signed the Metre Convention in 1875 and has legally defined its inch in metric terms since 1959. So why does it still sell milk in gallons?
When Unit Conversion Goes Wrong: Four Expensive Failures
A lost Mars orbiter, an airliner out of fuel at 41,000 feet, a cancelled rocket launch and a fatal overdose — all traced to unit errors.
Cooking Conversions: Why Professionals Weigh Everything
A cup of flour can vary by 30% depending on how you fill it. Here is why volume measurement fails in baking and how to convert recipes reliably.
Why Your 1 TB Drive Shows 931 GB: The GB vs GiB Problem
Your drive is not lying and neither is your operating system. They are using two different definitions of the same word.
MPG vs L/100km: The Inverse Relationship That Fools Everyone
Improving from 10 to 20 MPG saves more fuel than improving from 30 to 60 MPG. This is not a trick — it is what happens when you average a reciprocal.
How the Kilogram Was Redefined in 2019 (And Why It Had To Be)
For 130 years the kilogram was a lump of metal in a vault near Paris. Then it started losing weight — and nobody could prove it.
Converter categories, from everyday length to radiology dose
Individual units, each with an exact published factor
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