Quick Start

Use the calculators, try your own equation, or convert units. No account is needed for these basics.

Solve a calculation

  1. Open a calculator from Calculators.
  2. Select the variable you want to find in the Solve column.
  3. Enter the known values using the units shown, then click Calculate.
  4. To work backward, select a different unknown and enter the other known values.

Try it: In Ohm’s Law, select resistance as the unknown. For a 5 V supply, a 2 V LED, and a target current of 12 mA, enter 5-2 for voltage and 12m for current. The result is 250 Ω. Click the 249 Ω E96 suggestion, then solve for current to check the real resistor.

Watch the LED resistor calculation, then check the current using the suggested E96 value.

Try your own equation

Open Arbitrary, enter a LaTeX equation such as V=I R, and click Parse. Check the detected variables and choose their units, select the unknown, enter the known values, and click Calculate. You can use the equation without saving a calculator.

Convert units

Open Convert and type a query such as 1 inch in mm or 100 km/h to mph. Press Enter to save it to this browser’s conversion history.

Tips and tricks

  • Calculate in the input: Use 5-2, (10+5)/3, 2^3, or sqrt(16) instead of calculating separately.
  • Use SI prefixes: 10k means 10,000, 12m means 0.012, and 100u means 0.0001. Case matters: M is mega; m is milli. Match the displayed units; use Convert when changing between unit systems.
  • Combine components: In a resistance field, 10k || 10k gives 5 kΩ. In a capacitance field with units of F, 100n || 100n gives 200 nF.
  • Enter time ranges: 9am - 5pm gives 8 hours. Add work periods with +, for example 8am - 2pm + 3pm - 5pm. Each period must end on the same day.
  • Check tolerances: Enable Tolerance Mode and enter input percentages to see RSS (root sum square) and worst-case estimates.
  • Keep your work: Use Share Link to copy a calculation with its inputs, or Create Permalink for a shorter link. In Convert, use Create Permalink.
  • Move to a spreadsheet: Spreadsheet Mode provides output to copy into Excel or Google Sheets.

About Equation Engine