Inverse Proportion Rule

Solve inverse proportion problems. When two quantities are inversely proportional, their product remains constant. Enter three known values to find the fourth.

a × b = c × d

Enter 3 values to find the 4th

Why use this tool?

Inverse proportion is used when one quantity increases while another decreases. This tool helps you solve these problems quickly.

  • Simple interface — enter three values and get the fourth instantly.
  • Shows the formula — understand how the calculation works.
  • Privacy-focused — all calculations happen in your browser. No data is sent to servers.
  • Fast and free — no sign-up required, instant results.

How to use

  1. Enter three of the four values where a × b = c × d.
  2. Leave the field blank for the value you want to calculate.
  3. Click Calculate to see the result.
  4. View the calculated value and the formula used.
  5. Click Copy Result to copy the answer to your clipboard.

Frequently Asked Questions

Inverse proportion occurs when one quantity increases while the other decreases at the same rate. Mathematically, if a × b = c × d, then as one value increases, the other must decrease to maintain the same product.

Yes, the MushTools Inverse Proportion calculator is completely free with no sign-up required. All calculations happen in your browser.

No. Everything runs client-side in your browser. Your data is not stored or sent to any server.