Free Unit Converters — Length, Weight, Temperature, and CSS Units Online
Free unit converters for length, weight, temperature, speed, area, volume, pressure, energy, force, and CSS units including px, rem, em, and percent.
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In This Collection
Length Converter
Weight Converter
Temperature Converter
PX to REM Converter
REM to PX Converter
Why this collection exists
Convert between any units of measurement instantly in your browser. Physical units for science and engineering, and CSS units for frontend development — all in one place.
Unit Converters covers both everyday conversions (kilometres to miles, kilograms to pounds, Celsius to Fahrenheit) and developer-specific conversions (px to rem, em to percent, points to pixels) that come up constantly in frontend work.
Best fit for
- Frontend developers converting CSS units
- Students and engineers working with SI and imperial units
- Designers converting between px, rem, em, and pt
- Anyone needing quick unit conversions without a calculator
Featured tools in this collection
Start with the strongest tools in this workflow cluster.
Length Converter
Convert length units between meters, kilometers, inches, feet, yards, miles, nautical miles, and metric subunits.
Weight Converter
Convert common weight units between grams, kilograms, ounces, pounds, stones, tons, and carats.
Temperature Converter
Convert temperature units between Celsius, Fahrenheit, Kelvin, Rankine, and Reaumur.
PX to REM Converter
Convert pixel values to REM units instantly. Set your base font size, enter one or multiple px values, and get the REM equivalent with a full reference table.
REM to PX Converter
Convert REM values to pixels instantly. Set your base font size, enter one or multiple REM values, and get the pixel equivalent with a full reference table.
PX to EM Converter
Convert pixel values to EM units instantly. Set the parent element font size, enter one or multiple px values, and get the EM equivalent with a full reference table.
Tools by Workflow
Browse tools grouped by what you need to get done.
Physical Unit Converters
Convert length, weight, temperature, speed, area, volume, pressure, energy, and more.
Length Converter
Convert length units between meters, kilometers, inches, feet, yards, miles, nautical miles, and metric subunits.
Weight Converter
Convert common weight units between grams, kilograms, ounces, pounds, stones, tons, and carats.
Temperature Converter
Convert temperature units between Celsius, Fahrenheit, Kelvin, Rankine, and Reaumur.
Speed Converter
Convert speed units between m/s, km/h, mph, ft/s, knots, Mach, cm/s, and km/s.
Area Converter
Convert area units between square meters, square feet, acres, hectares, square miles, and more.
Volume Converter
Convert volume units between mL, L, cubic meters, cubic feet, US cooking units, US gallons, and imperial gallons.
Mass Converter
Convert mass units between grams, kilograms, metric tons, ounces, pounds, stones, tons, and carats.
Pressure Converter
Convert pressure units between Pa, kPa, MPa, bar, mbar, atm, psi, Torr, mmHg, and inHg.
Energy Converter
Convert energy units between J, kJ, cal, kcal, Wh, kWh, BTU, eV, and ft-lb.
Power Converter
Convert power units between watts, kilowatts, megawatts, horsepower, BTU per hour, ft-lb/s, and calorie rates.
Force Converter
Convert force units between N, kN, dyn, kgf, lbf, ozf, pdl, and kip.
Density Converter
Convert density units between kg/m^3, g/cm^3, g/L, kg/L, lb/ft^3, lb/in^3, and lb/gal.
Frequency Converter
Convert frequency units between Hz, kHz, MHz, GHz, CPM, RPM, BPM, and rad/s.
Fuel Converter
Convert fuel economy and fuel consumption units between mpg, km/L, L/100 km, and gallons per 100 miles.
Electric Current Converter
Convert electric current units between A, mA, uA, nA, kA, and MA with adjustable precision.
Astronomical Converter
Convert astronomical distances between AU, light-years, parsecs, light-seconds, lunar distances, and more.
CSS Unit Converters — px, rem, em
Convert between px, rem, em, percent, and point CSS units for responsive design.
PX to REM Converter
Convert pixel values to REM units instantly. Set your base font size, enter one or multiple px values, and get the REM equivalent with a full reference table.
REM to PX Converter
Convert REM values to pixels instantly. Set your base font size, enter one or multiple REM values, and get the pixel equivalent with a full reference table.
PX to EM Converter
Convert pixel values to EM units instantly. Set the parent element font size, enter one or multiple px values, and get the EM equivalent with a full reference table.
EM to PX Converter
Convert EM values to pixels instantly. Set the parent element font size, enter one or multiple EM values, and get the pixel equivalent with a full reference table.
PX to Percent Converter
Convert pixel values to CSS percentage units. Set the parent element size, enter one or multiple px values, and get the percentage equivalent with a full reference table.
Percent to PX Converter
Convert CSS percentage values to pixels. Set the parent element size, enter one or multiple percent values, and get the pixel equivalent with a full reference table.
PX to Point Converter
Convert pixel values to CSS/print point (pt) units instantly. Uses the standard 96dpi formula: 1pt = 96/72 px. Supports bulk input and includes a reference table.
Point to PX Converter
Convert CSS/print point (pt) values to pixels. Uses the standard 96dpi formula: 1pt = 96/72 px ≈ 1.3333px. Supports bulk input and includes a reference table.
EM to Percent Converter
Convert CSS EM values to percentage. For font-size, 1em = 100% — a direct 1:1 relationship. Supports bulk input and includes a reference table.
Percent to EM Converter
Convert CSS percentage values to EM units. For font-size, 100% = 1em — a direct relationship. Supports bulk input and includes a reference table.
EM to Point Converter
Convert CSS EM values to typographic point (pt) units. Set the parent font size, enter EM values, and get the point equivalent. Useful for @media print stylesheets.
Point to EM Converter
Convert CSS/print point (pt) values to EM units. Set the parent font size, enter pt values, and get the EM equivalent. Useful for translating print sizes to screen CSS.
REM to Percent Converter
Convert CSS REM values to percentage. For root-relative sizing, 1rem = 100% of the root font size. Supports bulk input and includes a reference table.
Percent to REM Converter
Convert CSS percentage values to REM units. 100% = 1rem numerically. Supports bulk input and includes a reference table.
REM to Point Converter
Convert CSS REM values to typographic point (pt) units. Set the root font size, enter REM values, and get the point equivalent. Useful for @media print stylesheets.
Point to REM Converter
Convert CSS/print point (pt) values to REM units. Set the root font size, enter pt values, and get the REM equivalent. Useful for translating print sizes to screen CSS.
Inches to Pixels Converter
Convert inches to CSS pixels using the standard 96dpi formula (1in = 96px). Supports bulk input and includes a reference table from 1/16 inch to 10 inches.
Browse the supporting categories
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All tools in this collection
Browse the complete workflow cluster and jump into the tool you need next.
Length Converter
Convert length units between meters, kilometers, inches, feet, yards, miles, nautical miles, and metric subunits.
Weight Converter
Convert common weight units between grams, kilograms, ounces, pounds, stones, tons, and carats.
Temperature Converter
Convert temperature units between Celsius, Fahrenheit, Kelvin, Rankine, and Reaumur.
Speed Converter
Convert speed units between m/s, km/h, mph, ft/s, knots, Mach, cm/s, and km/s.
Area Converter
Convert area units between square meters, square feet, acres, hectares, square miles, and more.
Volume Converter
Convert volume units between mL, L, cubic meters, cubic feet, US cooking units, US gallons, and imperial gallons.
Mass Converter
Convert mass units between grams, kilograms, metric tons, ounces, pounds, stones, tons, and carats.
Pressure Converter
Convert pressure units between Pa, kPa, MPa, bar, mbar, atm, psi, Torr, mmHg, and inHg.
Energy Converter
Convert energy units between J, kJ, cal, kcal, Wh, kWh, BTU, eV, and ft-lb.
Power Converter
Convert power units between watts, kilowatts, megawatts, horsepower, BTU per hour, ft-lb/s, and calorie rates.
Force Converter
Convert force units between N, kN, dyn, kgf, lbf, ozf, pdl, and kip.
Density Converter
Convert density units between kg/m^3, g/cm^3, g/L, kg/L, lb/ft^3, lb/in^3, and lb/gal.
Frequency Converter
Convert frequency units between Hz, kHz, MHz, GHz, CPM, RPM, BPM, and rad/s.
Fuel Converter
Convert fuel economy and fuel consumption units between mpg, km/L, L/100 km, and gallons per 100 miles.
Electric Current Converter
Convert electric current units between A, mA, uA, nA, kA, and MA with adjustable precision.
Astronomical Converter
Convert astronomical distances between AU, light-years, parsecs, light-seconds, lunar distances, and more.
PX to REM Converter
Convert pixel values to REM units instantly. Set your base font size, enter one or multiple px values, and get the REM equivalent with a full reference table.
REM to PX Converter
Convert REM values to pixels instantly. Set your base font size, enter one or multiple REM values, and get the pixel equivalent with a full reference table.
PX to EM Converter
Convert pixel values to EM units instantly. Set the parent element font size, enter one or multiple px values, and get the EM equivalent with a full reference table.
EM to PX Converter
Convert EM values to pixels instantly. Set the parent element font size, enter one or multiple EM values, and get the pixel equivalent with a full reference table.
PX to Percent Converter
Convert pixel values to CSS percentage units. Set the parent element size, enter one or multiple px values, and get the percentage equivalent with a full reference table.
Percent to PX Converter
Convert CSS percentage values to pixels. Set the parent element size, enter one or multiple percent values, and get the pixel equivalent with a full reference table.
PX to Point Converter
Convert pixel values to CSS/print point (pt) units instantly. Uses the standard 96dpi formula: 1pt = 96/72 px. Supports bulk input and includes a reference table.
Point to PX Converter
Convert CSS/print point (pt) values to pixels. Uses the standard 96dpi formula: 1pt = 96/72 px ≈ 1.3333px. Supports bulk input and includes a reference table.
EM to Percent Converter
Convert CSS EM values to percentage. For font-size, 1em = 100% — a direct 1:1 relationship. Supports bulk input and includes a reference table.
Percent to EM Converter
Convert CSS percentage values to EM units. For font-size, 100% = 1em — a direct relationship. Supports bulk input and includes a reference table.
REM to Percent Converter
Convert CSS REM values to percentage. For root-relative sizing, 1rem = 100% of the root font size. Supports bulk input and includes a reference table.
Percent to REM Converter
Convert CSS percentage values to REM units. 100% = 1rem numerically. Supports bulk input and includes a reference table.
EM to Point Converter
Convert CSS EM values to typographic point (pt) units. Set the parent font size, enter EM values, and get the point equivalent. Useful for @media print stylesheets.
Point to EM Converter
Convert CSS/print point (pt) values to EM units. Set the parent font size, enter pt values, and get the EM equivalent. Useful for translating print sizes to screen CSS.
REM to Point Converter
Convert CSS REM values to typographic point (pt) units. Set the root font size, enter REM values, and get the point equivalent. Useful for @media print stylesheets.
Point to REM Converter
Convert CSS/print point (pt) values to REM units. Set the root font size, enter pt values, and get the REM equivalent. Useful for translating print sizes to screen CSS.
Inches to Pixels Converter
Convert inches to CSS pixels using the standard 96dpi formula (1in = 96px). Supports bulk input and includes a reference table from 1/16 inch to 10 inches.
Collection FAQ
Extra context around when to use this toolkit and where to start.
How do I convert px to rem in CSS?
Use px to rem Converter. Enter a pixel value and it calculates the rem equivalent based on a configurable base font size (default 16px). The formula is: rem = px ÷ base-font-size. rem units scale with the user's browser font size preference, making them better for accessibility than fixed px values.
What is the difference between rem and em in CSS?
rem (root em) is always relative to the root element font size (usually 16px). em is relative to the font size of the nearest parent element, which can compound unpredictably in nested elements. rem is generally preferred for font sizes and spacing because it is more predictable.
How do I convert Celsius to Fahrenheit?
Use Temperature Converter. Enter a value in Celsius, Fahrenheit, or Kelvin and it instantly converts to all three. The formula is: °F = (°C × 9/5) + 32.
How do I convert kilometres to miles?
Use Length Converter. Enter a value in any length unit — kilometres, metres, miles, feet, inches, yards, nautical miles — and it converts to all supported units simultaneously.
How do I convert px to percent in CSS?
Use px to percent Converter. Enter the element pixel width and the parent container width. It calculates the percentage value so you can replace fixed widths with fluid, responsive percentages.
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