Free Unit Converters
Length, weight, volume, energy, pressure and the specialist quantities — built on exact SI definitions rather than rounded constants.
65 free tools · no signup
Acceleration Converter
Convert acceleration between m/s2, g-force, ft/s2, km/h/s, mph/s, Gal and milligal.
Area Converter
Convert square meters, acres, hectares, square feet, and more instantly with exact factors.
Aspect Ratio Calculator
Simplify width/height to a ratio, or solve a missing dimension for a target ratio.
Bandwidth Converter
Convert bps, Kbps, Mbps, Gbps, KB/s, and MB/s, plus calculate download time for any file size.
Capacitance Converter
Convert capacitance between farads, microfarads, nanofarads, picofarads and older CGS units.
Celsius to Fahrenheit Converter
Convert Celsius to Fahrenheit or Fahrenheit to Celsius instantly with the exact formula and a full reference table.
Clothing Size Converter
Convert clothing sizes between US, UK, EU and international scales for women's and men's wear.
Cm to Inches Converter
Convert centimetres to inches or inches to cm instantly with the exact 2.54 factor, a reference table, and a height calculator.
Concentration Converter
Convert mass concentration, molar concentration and mass fraction with a molar mass you enter.
Cooking Measurement Converter
Convert cups, tablespoons, teaspoons, ml, and liters, plus grams for common ingredients.
Currency Format Converter
Format any number as currency for any country using Intl.NumberFormat.
DPI/PPI Calculator
Calculate true screen PPI from resolution and size, or the max print size for an image at a target DPI.
Data Storage Converter
Convert bits, bytes, KB/MB/GB/TB (decimal) and KiB/MiB/GiB/TiB (binary) instantly.
Date Format Converter
Convert one date into ISO 8601, RFC 2822, US, European, long-form, and custom patterns at once.
Electric Charge Converter
Convert electric charge between coulombs, amp-hours, milliamp-hours and elementary charges.
Energy Converter
Convert joules, calories, kilocalories, watt-hours, kWh, BTU and therms instantly and accurately.
Flow Rate Converter
Convert flow rate between L/s, L/min, m³/h, US/imperial GPM, CFM, and barrels per day.
Force Converter
Convert newtons, kilonewtons, dynes, pound-force, kilogram-force and poundals instantly.
Fuel Economy Converter
Convert US MPG, Imperial MPG, L/100km, km/L, and miles per liter instantly and correctly.
Grams to Ounces
Convert grams to ounces instantly with a pounds-and-ounces breakdown, both directions.
Heat Flux Converter
Convert heat flux density between watts per square metre, BTU units, calories and langleys.
Inductance Converter
Convert any inductance value between henry, mH, µH, nH, pH and the older CGS units.
Joules to Calories Converter
Convert joules, calories, kilocalories, and kJ; understand the food Calorie.
Kg to Pounds Converter
Convert kilograms to pounds or pounds to kg instantly with the exact 0.45359237 factor and a full reference table.
Km to Miles Converter
Convert kilometres to miles or miles to km instantly with the exact 1.609344 factor and a full reference table.
Length Converter
Convert between metric and imperial length units instantly — mm to inches, km to miles, and more.
Liters to Gallons
Convert liters to US and imperial gallons instantly, both directions, with a full reference table.
Luminous Flux Converter
Convert luminous flux between lumens, kilolumens, candela-steradians and spherical candlepower.
Luminous Intensity Converter
Convert luminous intensity, flux, illuminance and luminance between candela, lumen, lux and nit.
MPH to KM/H Converter
Convert mph to km/h and back instantly, with a reference table and speed limits by country.
Magnetic Field Converter
Convert magnetic flux density, field strength and flux between tesla, gauss, A/m and weber.
Mass Flow Rate Converter
Convert mass flow rate between kilograms, pounds and tonnes per second, minute or hour.
Meters to Feet
Convert meters to feet instantly with automatic feet-and-inches breakdown, both directions.
Molar Mass Converter
Enter a chemical formula to get its molar mass, then convert grams, moles and molecules.
Note Frequency Converter
Convert musical notes to frequencies and frequencies to the nearest note with cents deviation.
Number Base Converter
Convert between binary, octal, decimal, hexadecimal, and any custom base 2-36, all at once.
PSI to Bar Converter
Convert PSI, bar, kPa, and atmospheres with a tire pressure reference table.
Paper Size Converter
Convert A4, Letter, and every ISO/North American paper size to mm, cm, in, px.
Permeability Converter
Convert magnetic permeability in H/m or fluid permeability in darcy, kept strictly separate.
Power Converter
Convert watts, kilowatts, mechanical and metric horsepower, BTU/hr and ft-lb/s instantly.
Pressure Converter
Convert Pascal, kPa, bar, psi, atm, torr and inHg instantly using exact SI-based factors.
Px to Rem Converter
Convert px to rem, em, pt, and percent instantly with a bulk list converter and configurable root size.
Radiation Dose Converter
Convert absorbed dose, equivalent dose, activity and exposure between SI and legacy units.
Resistance Converter
Convert electrical resistance between ohms, its SI prefixes, and the older CGS units.
Ring Size Converter
Convert ring sizes between US, UK, EU, and Japan and get exact diameter in mm.
Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers, instantly, both directions.
Shoe Size Converter
Convert shoe sizes across US, UK, EU, and CM for men, women, and kids.
Sound Level Converter
Convert decibel sound pressure, intensity and power levels to pascals and watts.
Specific Heat Converter
Convert specific, molar and volumetric heat capacity across SI, calorie and BTU units.
Speed Converter
Convert m/s, km/h, mph, knots, feet per second, and Mach instantly with exact factors.
Surface Tension Converter
Convert surface tension between newtons per metre, dynes per centimetre and imperial units.
Temperature Converter
Convert Celsius, Fahrenheit, Kelvin, and Rankine instantly with exact offset formulas, not simple ratios.
Thermal Conductivity Converter
Convert thermal conductivity between SI, calorie and BTU units and get the R-value for a thickness.
Time Converter
Convert nanoseconds through centuries — seconds, minutes, hours, days, weeks, months, years.
Timezone Converter
Convert any date and time between 40+ world timezones, DST included.
Tire Size Calculator
Decode a tire size code into diameter, circumference, and speedometer error.
Unix Timestamp Converter
Convert Unix epoch timestamps to human dates and back, seconds or milliseconds, UTC and local.
Viscosity Converter
Convert dynamic viscosity in Pa s, poise and cP, or kinematic viscosity in m2/s and cSt.
Volume Converter
Convert volume units instantly, including the key difference between US and imperial gallons and fluid ounces.
Watts to Horsepower Converter
Convert watts/kW to mechanical horsepower and metric horsepower (PS).
Weight Converter
Convert between metric and imperial weight units instantly — kilograms, pounds, ounces, stone, and more.
⚖️ Density Converter
Convert density instantly between kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ and oz/gal.
⚙️ Torque Converter
Convert torque instantly between N·m, kN·m, lb-ft, lb-in, kgf·m and oz-in.
⚡ Frequency Converter
Convert Hz, kHz, MHz, GHz, THz, RPM, BPM, and rad/s instantly, free.
📐 Angle Converter
Convert degrees, radians, gradians, arcminutes, arcseconds, turns & milliradians instantly.
Exact factors, not approximations
Where a conversion is defined exactly, these tools use the exact definition: an inch is 25.4 millimetres, standard gravity is 9.80665 m/s², a calorie has a specific value that depends on which calorie you mean. Rounded constants compound quickly across multi-step conversions, which is why every converter here also publishes a reference table of its factors relative to the SI base unit so you can check the arithmetic yourself.
The quantities people conflate
Several of these tools exist because two different physical quantities share a name. Dynamic viscosity and kinematic viscosity are related only through density and cannot be interconverted without it. Absorbed dose and equivalent dose differ by a radiation weighting factor. Luminous intensity is per steradian; luminous flux is not. Magnetic permeability and the permeability of a porous medium are unrelated despite the shared word. Each of those tools separates the modes so a cross-quantity conversion is structurally impossible rather than merely discouraged.
Logarithmic units behave differently
Decibels do not add linearly — doubling the sound power adds about 3 dB, not double the number. The sound-level converter states its reference values and explains the rule rather than treating dB as an ordinary unit.
