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Ratio Calculator

Enter a ratio and this calculator simplifies it to its lowest terms, solves for a missing value in a pair of equivalent ratios (A:B = C:?), or splits any total amount by a ratio — with the exact working shown. It runs entirely in your browser: free, instant, and no sign-up.

Fill in the fields to see the result with the working shown.

Frequently asked questions

Divide both sides of the ratio by their greatest common divisor (GCD). For example, 12:18 has a GCD of 6, so it simplifies to 2:3. This calculator does it instantly — enter the two numbers and it shows the simplified ratio, the GCD used, and the decimal ratio (1:n) form.

Equivalent ratios have equal cross-products: if A:B = C:D, then A × D = B × C. So the missing D is B × C ÷ A. Enter the three known values and the calculator solves the fourth, showing the working.

Add the ratio parts to get the total number of shares, divide the amount by that total to get one share, then multiply by each part. For example, $100 split 2:3 is 5 shares of $20 — so $40 and $60. The split mode does this for you and shows each share and its percentage.

Yes — free, no sign-up, and all the math runs in your browser, so nothing you enter is uploaded or stored anywhere.