Math Calculators
Percent, fractions, number bases and geometry — math calculators for study and work.
How to choose a tool
Use the percentage calculator for a part of a whole and percentage change for the relative change from an old value to a new one. Use the fraction calculator for fraction arithmetic and proportion for a missing value in two ratios. Base and temperature tools change representations, while circle, triangle, and rectangle tools use lengths to find perimeter or area.
If a value rises from 80 to 100, the difference is 20 but the increase relative to 80 is 25%. Enter width and height in the same unit for aspect ratio, and do not confuse radius with diameter or base with height. First decide whether the question asks for a ratio or an actual amount and confirm matching units.
How to verify the result
Check signs, decimals, and length or temperature units before calculating. Read the displayed formula and intermediate values, then substitute the result back when possible. Simple checks—25% of 80 is 20, or a circle's diameter is twice its radius—quickly reveal input and unit errors.
Displayed precision and rounding can make the last digit differ from hand calculations. Concentration, proportions, and geometry are valid only under the entered assumptions and do not remove measurement error. They work for learning and drafts, but contracts, exam answers, and manufacturing dimensions should be recalculated using the required rounding rule and primary data.