From working out a discount to checking an algebra problem, these tools cover the arithmetic and school-level maths people reach for most. Each page explains the formula behind the answer and the mistakes that most often produce a wrong one, such as dividing by the wrong base in a percentage change or forgetting the sign of b in the quadratic formula.
If you're unsure which percentage tool you need, ask what the question is. Use the Percentage Calculator for "what is X% of Y", Percentage Change when a value moved from one number to another, Percentage Increase for growth specifically, and Percent Error when you're comparing a measurement against a known true value.
Arithmetic & Percentages
Any percentage calculation
Percentage Change Calculator% change between original and new value
Percentage Increase Calculator% increase between two numbers
Percent Error CalculatorPercent error against a true value
Ratio CalculatorSimplify and solve ratios
Average CalculatorArithmetic mean of any set
Fraction CalculatorAdd, subtract, multiply, divide fractions
Mixed Number CalculatorAdd and subtract mixed numbers
Decimal to Fraction CalculatorConvert a decimal to a fraction
Long Division CalculatorLong division with remainder
8x8 CalculatorMultiply any two numbers and the 8 times table
Algebra & Calculus
Solve equations step by step
Quadratic Formula CalculatorSolve ax² + bx + c = 0
Exponent CalculatorPowers and roots of any number
Logarithm CalculatorLogarithms in any base
Radical CalculatorSimplify radicals and roots
Square Root CalculatorExact and decimal square roots
Partial Derivative CalculatorPartial derivatives of a function
Scientific CalculatorTrig, logs, exponents & more
Graphing CalculatorPlot a function on a graph
Geometry & Measurement
Find any side of a right triangle
Triangle CalculatorSides, angles and area of a triangle
Distance Formula CalculatorDistance between two coordinate points
Slope CalculatorSlope and line equation from two points
Area CalculatorArea of any shape
Volume CalculatorVolume of common 3D shapes
Speed Distance Time CalculatorSolve for speed, distance or time
Statistics & Probability
Mean, median, mode, standard deviation
Z-Score CalculatorStandard score & percentile
Probability CalculatorSingle and compound probability
Number Systems & Notation
Binary, decimal, hex
Roman Numeral ConverterConvert to/from Roman numerals
Prime Number CheckerIs it prime?
Scientific Notation CalculatorConvert & multiply large numbers
Significant Figures CalculatorCount and round significant figures
Results are computed in your browser with standard floating-point arithmetic, so very long decimals are rounded for display. For homework, work the problem by hand first and use the calculator to check it; the explanations on each page are written to help you find where a hand calculation went wrong.