Math Tools
Percentages, averages, fractions, ratios and statistics — solved instantly.
Everyday math tools that give exact answers instantly. Work out percentages and percentage change, simplify and compare fractions, compute averages, standard deviation and probabilities, and check ratios — all with the formulas shown on the page so you can verify the result yourself.
All tools
Percentage Calculator
Percentage of a number, what percent one value is of another, and percentage change.
Percentage Increase Calculator
Find the percent increase between two values and the amount added.
Percentage Decrease Calculator
Calculate the percent drop between two values, or the increase if it rose.
Percentage Difference Calculator
Compare two numbers as a percent difference based on their average.
Fraction Calculator
Add, subtract, multiply and divide fractions with simplified results.
Ratio Calculator
Simplify a ratio and solve missing ratio values.
Average Calculator
Find the mean, sum and count of any list of numbers.
Weighted Average Calculator
Compute an average where some values matter more than others.
Standard Deviation Calculator
Measure how spread out your numbers are, population or sample.
Probability Calculator
Turn favorable and total outcomes into a probability.
10 tools · updated continuously
How these tools work
Everyday math tools that give exact answers instantly. Work out percentages and percentage change, simplify and compare fractions, compute averages, standard deviation and probabilities, and check ratios — all with the formulas shown on the page so you can verify the result yourself. Every tool in this category publishes its formula, worked example and assumptions so you can verify the result yourself.
Frequently asked questions
Are these math tools accurate?
Yes. Every tool runs a documented formula with automated unit tests that cover zero, negative and extreme inputs. The formula and a worked example are published on each page.
Can I use the calculators on mobile?
Absolutely. All tools are responsive and run entirely in your browser, so they work on any phone or tablet without installing anything.
What does percentage change use as the base?
Percentage change is (New − Old) ÷ |Old| × 100. The original value is taken as the base using its absolute value, so a drop from 10 to 5 is −50%.