Math calculators
Tools that give an exact result, then show the formula. Each page spells out edge cases (division by zero, impossible triangles, rounding).
These calculators cover everyday arithmetic (percentages, averages, ratios) and a few plane-geometry tools. The math is deterministic: the same input always yields the same output.
Most used
- PercentageEnter two numbers of the same kind. The tool returns (part ÷ total) × 100 — useful for a test score, a slice of a budget, or a share of a count.
- Percent increaseGive a starting amount and a higher later amount. The tool reports the rise relative to the start, not a “neutral” gap between two figures.
- Percent decreaseEnter an original amount and a smaller later amount. The result is the drop relative to the original — the same idea as a markdown, without applying a sale price formula.
- Percent differenceA and B are not labeled “before” and “after.” You get the absolute gap, the gap relative to A, relative to B, and the symmetric gap (divided by the average). That is not a percent increase.
Subcategories
Percentages
Share of a total, increase, decrease and relative gap.
Numbers and arithmetic
Fractions, ratios, GCF, LCM, roots and powers.
Full list
- PercentageEnter two numbers of the same kind. The tool returns (part ÷ total) × 100 — useful for a test score, a slice of a budget, or a share of a count.
- Percent increaseGive a starting amount and a higher later amount. The tool reports the rise relative to the start, not a “neutral” gap between two figures.
- Percent decreaseEnter an original amount and a smaller later amount. The result is the drop relative to the original — the same idea as a markdown, without applying a sale price formula.
- Percent differenceA and B are not labeled “before” and “after.” You get the absolute gap, the gap relative to A, relative to B, and the symmetric gap (divided by the average). That is not a percent increase.
- FractionsTwo integer fractions and an operation. The engine uses a common denominator or cross-products, then reduces by the GCF so the answer is in lowest terms.
- RatioTwo integers in, a reduced ratio out (8 : 12 becomes 2 : 3), plus the quotient A/B and each term’s weight in the sum of absolute values — not “A as a percent of B.”
- AveragePaste numbers; the tool sums, counts, and divides. Every observation has weight 1. Min, max, and count sit beside the mean.
- Weighted averageEach line is a value and its coefficient. The mean is the sum of (value × weight) divided by the sum of weights — not the average of the values then of the weights.
- GCF (GCD)Enter at least two integers. The result is the largest positive integer that divides all of them — the same GCF used to reduce a fraction or a ratio.
- LCMEnter at least two nonzero integers. The result is the smallest positive integer that is a multiple of each — useful for common denominators and repeating schedules.
- Square rootEnter a number that is not negative. The tool returns the principal (nonnegative) square root. It is the inverse of squaring, not a cube root or an nth root.
- ExponentEvaluate aᵇ. Integers, decimals, negative exponents (reciprocals), and 1/2 (square root, base ≥ 0) are possible, within the reals and floating-point limits.
- Pythagorean theoremTwo modes: √(a² + b²) for the hypotenuse, or √(c² − a²) for the missing leg. The triangle must be right-angled; a “leg” longer than the hypotenuse is rejected.
- Circle areaOne length is enough: the radius, or the diameter (halved). You get area πr², circumference 2πr, and both r and d as a check.
- Triangle areaPick the data you have: a base and its perpendicular height, three side lengths, or two sides and the included angle. A collapsed (zero-area) triangle is rejected.
- Speed, distance, timeTwo known quantities, the third follows. Kilometres and km/h, or miles and mph, but not a mix of the two systems.
Questions
Are results rounded?
Internal math uses JavaScript floating point. The display rounds for reading (often 2 to 4 decimals). Each tool page states the rounding rule.
Can I use a comma as the decimal separator?
Yes. 12.5 and 12,5 are accepted. For a list of numbers, separate values with new lines or semicolons.