Percentages, algebra, geometry, fractions, statistics and general math problem solving. All tools are free and work directly in your browser.
Popular tools people often start with in this category.
Solve common percentage questions: find a percentage of a number, determine what percent one number is of another, and calculate a value from a known percentage.
Add, subtract, multiply or divide two fractions and reduce the result to lowest terms.
Calculate mean, variance and standard deviation for a sample or an entire population.
Round numbers and estimate arithmetic before checking the exact answer.
Browse the complete set of tools in this category.
Find the arithmetic mean of a comma-separated list of numbers.
Calculate circumference and area from a circle radius.
Calculate combinations nCr: the number of ways to choose r items from n when order does not matter.
Calculate cone volume, slant height and total surface area from radius and vertical height.
Calculate the volume and total surface area of a right circular cylinder.
Convert a terminating decimal to a reduced fraction and mixed number.
Calculate straight-line distance between two points on a 2D coordinate plane.
Add, subtract, multiply or divide two fractions and reduce the result to lowest terms.
Find the greatest common factor (greatest common divisor) of two or more whole numbers.
Find the least common multiple of two or more whole numbers.
Find the mean, median, mode and range of a list of numbers.
Find the midpoint between two points on a coordinate plane.
Find the cumulative probability below, above or between values in a normal distribution.
Calculate percentage increase or decrease from an original value to a new value.
Calculate symmetric percent difference between two values without treating either one as the original value.
Calculate percent error between an experimental or measured value and an accepted value.
Solve common percentage questions: find a percentage of a number, determine what percent one number is of another, and calculate a value from a known percentage.
Calculate permutations nPr: the number of ordered arrangements of r items chosen from n.
Break a positive whole number into its prime factors.
Calculate the probability of one event, its complement, and simple independent AND/OR combinations.
Solve a proportion of the form a/b = c/d when one of the four values is unknown.
Find the hypotenuse of a right triangle from the two perpendicular side lengths.
Solve a quadratic equation in the form ax² + bx + c = 0 and identify real or complex roots.
Simplify a ratio of two whole numbers to lowest terms.
Calculate area, perimeter and diagonal of a rectangle from length and width.
Solve a right triangle from two side lengths and find the hypotenuse, angles, area and perimeter.
Convert a number to normalized scientific notation and evaluate a coefficient times a power of ten.
Find the slope of the line through two coordinate points.
Calculate the volume and surface area of a sphere from its radius.
Calculate mean, variance and standard deviation for a sample or an entire population.
Calculate triangle area using a base and perpendicular height.
Calculate a z-score from a value, mean and standard deviation.
Round numbers and estimate addition, subtraction, multiplication or division before comparing with the exact answer.
Use common scientific functions including powers, roots, logarithms, exponentials and trigonometric functions.
Calculate square roots and nth roots, including exact decimal results for positive and negative values when defined.
Calculate a base raised to an exponent and see the reciprocal form for negative exponents.
Generate one or more random numbers within a selected minimum and maximum range.
Calculate triangle perimeter from three side lengths and validate the triangle.
Percentages, algebra, geometry, fractions, statistics and general math problem solving. Use these tools for quick estimates, comparisons and everyday planning.
From percentages and fractions to geometry, algebra and statistics, ERICH Calculators groups practical math tools into one simple library.
Explore focused calculator clusters with related tools, formulas, examples and long-tail guides.
Percentage change, discounts, tax, tips and everyday percent-of-number questions.
Explore topic →MathFraction arithmetic, decimal-to-fraction conversion, ratios and proportions.
Explore topic →MathAverages, standard deviation, z-scores, normal distributions and probability calculations.
Explore topic →MathRight triangles, areas, slopes, distances and common coordinate-geometry formulas.
Explore topic →Learn the method behind popular calculators in this category.
Percentage change is one of the most common ways to compare an old value with a new one. The same basic method works for prices, grades, revenue, wages, measurements and many other everyday numbers.
Read guide →StatisticsStandard deviation measures how spread out a set of numbers is around its mean. A small standard deviation means the values tend to stay close to the average; a larger one indicates more dispersion.
Read guide →For a percentage of a number, multiply by the percentage as a decimal: 15% of 80 is 0.15 × 80 = 12. For a percentage change, divide the change by the original value before multiplying by 100. If you need to check a calculation before finding an exact result, round its inputs to easy numbers and then use the estimation tool. Geometry questions need the correct unit and formula: area is measured in square units, while perimeter is a length.