Free Unit Converters

Length, weight, volume, energy, pressure and the specialist quantities — built on exact SI definitions rather than rounded constants.

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Most visited in Converters

Shoe Size Converter Convert shoe sizes across US, UK, EU, and CM for men, women, and kids. Meters to Feet Convert meters to feet instantly with automatic feet-and-inches breakdown, both directions. Grams to Ounces Convert grams to ounces instantly with a pounds-and-ounces breakdown, both directions. DPI/PPI Calculator Calculate true screen PPI from resolution and size, or the max print size for an image at a target DPI. Bandwidth Converter Convert bps, Kbps, Mbps, Gbps, KB/s, and MB/s, plus calculate download time for any file size.

Ordered by how often these pages are shown in Google Search results. Every tool in the category is listed in full below.

A 4 tools

Acceleration Converter Convert acceleration between m/s2, g-force, ft/s2, km/h/s, mph/s, Gal and milligal. Angle Converter Convert degrees, radians, gradians, arcminutes, arcseconds, turns & milliradians instantly. 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.

B 1 tool

Bandwidth Converter Convert bps, Kbps, Mbps, Gbps, KB/s, and MB/s, plus calculate download time for any file size.

C 7 tools

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.

D 4 tools

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. Density Converter Convert density instantly between kg/m³, g/cm³, g/mL, kg/L, lb/ft³, lb/in³ and oz/gal. DPI/PPI Calculator Calculate true screen PPI from resolution and size, or the max print size for an image at a target DPI.

E 2 tools

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.

F 4 tools

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. Frequency Converter Convert Hz, kHz, MHz, GHz, THz, RPM, BPM, and rad/s instantly, free. Fuel Economy Converter Convert US MPG, Imperial MPG, L/100km, km/L, and miles per liter instantly and correctly.

G 1 tool

Grams to Ounces Convert grams to ounces instantly with a pounds-and-ounces breakdown, both directions.

H 1 tool

Heat Flux Converter Convert heat flux density between watts per square metre, BTU units, calories and langleys.

I 1 tool

Inductance Converter Convert any inductance value between henry, mH, µH, nH, pH and the older CGS units.

J 1 tool

Joules to Calories Converter Convert joules, calories, kilocalories, and kJ; understand the food Calorie.

K 2 tools

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.

L 4 tools

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.

M 5 tools

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. MPH to KM/H Converter Convert mph to km/h and back instantly, with a reference table and speed limits by country.

N 2 tools

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.

P 6 tools

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. PSI to Bar Converter Convert PSI, bar, kPa, and atmospheres with a tire pressure reference table. Px to Rem Converter Convert px to rem, em, pt, and percent instantly with a bulk list converter and configurable root size.

R 4 tools

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.

S 5 tools

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.

T 6 tools

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. Torque Converter Convert torque instantly between N·m, kN·m, lb-ft, lb-in, kgf·m and oz-in.

U 1 tool

Unix Timestamp Converter Convert Unix epoch timestamps to human dates and back, seconds or milliseconds, UTC and local.

V 2 tools

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.

W 2 tools

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.

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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.

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