Percentage Calculator

How it works

Pick a mode: percent of a value, what percent X is of Y, increase or decrease by a percent, or percent change between two values. Enter numbers in the sentence-style fields and read the result instantly.

About Percentage Calculator

Informational only, not professional advice. Report an error.

A quiz says you got 42 out of 50 and you want the percentage without reaching for pencil and paper. Percent math shows up in test scores, survey results, sports stats, lab measurements, and simple before-and-after comparisons, and the same three patterns cover most everyday questions.

This calculator supports the modes people search most: percent of a number, what percent one number is of another, and percent change between two values. Pick a mode, enter values, and results update instantly. Percent change uses signed difference relative to the original starting value.

Percent change divides by the starting value, order matters. Going from 80 to 100 is +25%; going from 100 to 80 is −20%. What-percent mode fails gracefully on a zero denominator, which is useful when a dataset might contain empty totals.

Percent-of mode answers questions like what is 15% of 200 without rearranging the formula. Teachers grading on curves, students checking homework, and anyone comparing part-to-whole ratios all use what-percent mode, knowing that 42 out of 50 is 84% saves re-deriving the formula under time pressure.

Change mode fits before-and-after measurements: rainfall this month versus last month, practice test score improvements, or completion rates in a small project tracker. Always label which value is the baseline so readers know whether an increase or decrease is good in context.

Percents are unitless, which makes them portable across domains, but they can also hide scale. A 50% jump from 2 to 3 is very different from a 50% jump from 2,000 to 3,000 even though the percentage is identical, report the underlying numbers when precision matters.

For compound growth over many periods, repeated halving or doubling, or statistical margin of error, specialized tools apply different formulas. This page stays focused on single-step percent-of, what-percent, and change calculations you can verify by hand.

When sharing results in notes or slides, include direction language for change mode (increase versus decrease) and name the base in what-percent problems so nobody misreads which number was treated as the whole.

This tool is part of the free General collection on FindMeTool. Explore more General tools or browse the full tool directory.