Proportion Calculator is a free online tool that solves proportions right in your browser. It is built for students in the United States who need to check homework, for teachers who need a quick classroom check, and for parents who help with math at home. There is no sign-up, no download, and no account to create. Open the page, type your numbers, and read the answer with the steps shown.
What the Calculator Does
The proportion calculator on the home page has six modes, each for a different kind of problem:
- Solve: finds the one missing value when two ratios are equal, with every cross-multiplication step shown.
- Check: tests four numbers and answers TRUE or FALSE, with both cross products and both decimal values.
- Simplify: reduces a ratio such as 12:18 to 2:3 and shows the greatest common divisor used.
- Direct: solves word problems where both values move in the same direction, such as prices.
- Inverse: solves word problems where one value goes up while the other goes down, such as workers and days.
- Recipe scale: changes one ingredient amount when the number of servings changes.
How Your Numbers Are Handled
Every calculation happens in your browser. The numbers you type are not sent to a server, are not stored, and are not tied to an account, because there is no account. Closing the page removes the numbers from view, and nothing about your work is kept on this site.
Who This Site Is For
Students can check an answer before turning homework in and see where a setup went wrong. Teachers can work through an example on a classroom screen and show the cross-product check the class should use. Parents can follow the same steps the tool shows and help without guessing at the method. The wording stays plain throughout, and every result includes the steps, not just the final number.
What This Site Covers
This site covers proportion and ratio topics only. The tool and the guides stay on that subject: solving proportions, checking ratios, simplifying ratios, direct and inverse proportion, and scaling recipes, maps, and prices. It does not cover other branches of math, and it does not ask for personal information.