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Free Online Calculators
Use free online calculators for quick math, percentages, fractions, powers, roots, statistics, geometry, and everyday estimates. Start with the basic calculator when you need a large, simple keypad, then jump to a focused calculator when the job needs a formula.
Browse and filter calculatorsAll calculators
Choose a tool for your task. Open its matching guide when you need the inputs or results explained.
Basic CalculatorA clean browser calculator for quick arithmetic, percent checks, and copied results.Percentage CalculatorFind percent-of answers, percent change, discounts, and original values with reverse percentages.Ratio CalculatorSimplify ratios, scale matching ratios, and split totals by ratio parts.Percent Error CalculatorCompare your measured value with the accepted value, then see percent error and direction.Half-Life CalculatorCalculate remaining amount, elapsed time, or half-life with decay steps.Exponent CalculatorCalculate powers, zero and negative exponents, simple fraction exponents, and scientific notation.
Browse all 61 calculators
The 6 choices above and these 55 tools make up this category.
- Log CalculatorCalculate logarithms with custom bases, ln, log10, exponent checks, and change-of-base steps.
- Root CalculatorCalculate square roots, cube roots, nth roots, exponent form, real-number rules.
- Quadratic Formula CalculatorSolve quadratic equations with real or complex roots, discriminant, graph details, and steps.
- Binary CalculatorAdd, subtract, multiply, divide, and convert binary numbers.
- Hex CalculatorCalculate hex arithmetic, AND, OR, XOR, and base conversions with decimal and binary checks.
- Kawaii CalculatorA cute pastel calculator for quick everyday math.
- Scientific CalculatorA free scientific calculator for trig, inverse trig, logs, roots, powers, constants, and DEG/RAD mode.
- Fraction CalculatorCalculate, simplify, compare, and convert fractions, mixed numbers, whole numbers, and decimals with steps.
- Least Common Multiple CalculatorFind the least common multiple of positive whole numbers for fractions, schedules, and divisibility checks.
- Greatest Common Factor CalculatorFind the greatest common factor of two or more whole numbers with steps.
- Factor CalculatorList factors, factor pairs, and prime factorization for a whole number.
- Rounding CalculatorRound decimals, significant figures, and place values using clear method steps.
- Matrix CalculatorAdd, subtract, multiply, transpose, and find determinants for 2x2 and 3x3 matrices.
- Scientific Notation CalculatorConvert standard numbers to scientific notation or expand powers of 10 back to standard form.
- Big Number CalculatorAdd, subtract, multiply, and divide very large whole numbers exactly, then copy grouped or raw results and verify division remainders.
- Standard Deviation CalculatorCalculate sample or population standard deviation with variance, mean, count, and steps.
- Number Sequence CalculatorGenerate arithmetic, geometric, and Fibonacci-style sequences with formulas, next terms, and copyable results.
- Sample Size CalculatorEstimate survey sample size from confidence level, margin of error, and proportion.
- Probability CalculatorCalculate P(A or B), P(A and B), complements, and independent-event probability checks.
- Statistics CalculatorCalculate count, sum, mean, median, mode, range, quartiles, IQR, variance, and sample or population standard deviation.
- Mean, Median, Mode, Range CalculatorFind mean, median, mode, range, sorted values, sum, count, min, max, and quick steps for a list of numbers.
- Permutation and Combination CalculatorCalculate nPr and nCr for order-matters and order-does-not-matter counting problems.
- Z-score CalculatorCalculate a z-score and approximate standard normal percentile.
- Confidence Interval CalculatorCalculate z confidence intervals for a sample mean or sample proportion.
- Triangle CalculatorCheck three triangle sides, find a possible third-side range, or calculate SSS area, perimeter, angles, and type.
- Volume CalculatorFind cubic volume for boxes, cubes, cylinders, spheres, and cones.
- Slope CalculatorFind slope, rise, run, and a line equation from two points.
- Area CalculatorCalculate flat-shape area for rectangles, triangles, circles, trapezoids, and parallelograms.
- Distance CalculatorStraight-line distance between two 2D points, plus distance squared, deltas, midpoint, and formula steps.
- Circle CalculatorFind radius, diameter, circumference, and area from one circle measurement.
- Surface Area CalculatorCalculate surface area for boxes, cubes, cylinders, spheres, and cones.
- Pythagorean Theorem CalculatorSolve hypotenuse or missing leg lengths with a^2 + b^2 = c^2 and formula steps.
- Right Triangle CalculatorSolve a right triangle from two sides, including the missing side, area, perimeter, and acute angles.
- Absolute Value CalculatorFind absolute value, distance from zero, and absolute difference between two numbers.
- Prime Factorization CalculatorBreak a whole number into prime factors, prime powers, and factor checks.
- Long Division CalculatorDivide whole numbers with quotient, remainder, decimal answer, and steps.
- Average CalculatorFind the average (arithmetic mean) of a number list, then compare median, mode, range, sum, and count.
- P-value CalculatorEstimate left-tailed, right-tailed, or two-tailed standard-normal p-values from a z-score.
- Square Footage CalculatorCalculate square feet, square yards, and square meters from length, width, and quantity.
- Density CalculatorCalculate density from mass and volume with a custom unit label.
- Mass CalculatorCalculate mass from density and volume with unit-matching reminders.
- Weight CalculatorCalculate physics weight force from mass and gravity in newtons and pounds-force.
- Speed CalculatorCalculate average speed from distance and time in mph, km/h, and m/s.
- Voltage Drop CalculatorEstimate voltage drop from current, wire length, voltage, phase, and copper AWG size.
- Watts to Amps CalculatorConvert watts to amps at common 12 V, 120 V, and 240 V inputs with AC, DC, three-phase, and power-factor options.
- Amps to Watts CalculatorConvert amps to watts for DC, single-phase AC, and three-phase AC loads.
- Kilowatts to Amps CalculatorConvert kilowatts to amps with voltage, phase, power factor, and efficiency.
- kVA to Amps CalculatorConvert apparent power in kVA to amps for single-phase or three-phase systems.
- Amp Hours to Watt Hours CalculatorConvert battery amp-hours and voltage into watt-hours and kilowatt-hours.
- Watt Hours to Amp Hours CalculatorConvert battery watt-hours into amp-hours at a selected nominal voltage.
- Wire Resistance CalculatorEstimate copper wire resistance from AWG size, length, and conductor count.
- Wire Size CalculatorEstimate copper AWG size from a voltage-drop target.
- Stair CalculatorEstimate risers, treads, stair run, and angle from total rise and tread depth.
- Resistor CalculatorDecode 4-band resistor color codes into ohms, tolerance, minimum, and maximum values.
- Ohm's Law CalculatorSolve voltage, current, resistance, and power from two known circuit values.
Help choosing a tool and checking its results
Find the right calculator faster
Pick the path that matches the question you are trying to answer. It is faster than opening a giant list and guessing which page fits.
I just need a calculatorUse the basic calculator for quick arithmetic, decimals, and everyday keypad work.I need a percent answerUse the percentage calculator for discounts, tips, percent change, and markups.I need fraction helpCalculate, simplify, compare, or convert fractions, mixed numbers, whole numbers, and decimals.I need electrical unit mathConvert watts, volts, phase, and power factor into an amps estimate before reading the electrical safety limits.I am planning moneyStart with mortgage estimates, then browse finance calculators for more planning tools.
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Calculator paths by task
These links match the main ways people search for free calculators: simple everyday math, percentage problems, scientific functions, money estimates, health estimates, and unit conversion.
Start by task
Basic CalculatorLarge simple calculator for everyday addition, subtraction, multiplication, division, decimals, and percent checks.Percentage CalculatorPercent of a number, percent change, discounts, markups, and reverse percentage questions.Scientific CalculatorTrig, logarithms, powers, roots, constants, and degree/radian mode for heavier math.Finance CalculatorsMortgage, loan, salary, interest, retirement, tax, and investment planning estimates.Health & Fitness CalculatorsBMI, calories, pregnancy, nutrition, pace, body measurement, and educational health estimates.Conversion CalculatorCommon unit conversions when a calculator answer needs a different measurement unit.
Useful calculator shortcuts
Open these calculators when you need dates, fractions, geometry, matrices, or exact large-number work without hunting through the full library.
Useful shortcuts
Date CalculatorAdd days, subtract days, and count calendar differences without mixing start and end dates.Fraction CalculatorCalculate, simplify, compare, and convert fractions, mixed numbers, whole numbers, and decimals with visible steps.Area CalculatorFind common shape areas and compare formulas before trusting a measurement.Matrix CalculatorAdd, multiply, transpose, and check determinant-style matrix work in the browser.Triangle CalculatorSolve triangle sides, angles, perimeter, and area while checking impossible inputs.Big Number CalculatorHandle very large whole-number math when normal calculator precision is not enough.
What this category helps with
- Free online calculator pages for quick math checks, school work, percentage problems, fractions, powers, roots, and number theory.
- A simple basic calculator path for visitors who want a large browser keypad with no signup and no app install.
- Formula-based calculators that show enough context to understand the answer, not just copy it.
- Related blog guides that explain common mistakes, practical examples, and when to use a more specific calculator.
Guides for this category
Each guide uses its matching tool, with example numbers and plain limits.
- How to use the Basic CalculatorLearn the keypad, keyboard shortcuts, percent discounts, one-step math behavior, copy result action, and tab-only calculation history.
- Percentage Calculator Guide: Reverse PercentagesLearn three reverse-percentage setups, percent change, discounts, and how to recover an original value before an increase or decrease.
- Ratio Calculator GuideLearn how to simplify ratios, scale equivalent ratios, split totals, handle decimals, check units, and avoid swapped-part mistakes.
- Percent Error Calculator GuideLearn how to compare measured and accepted values, read signed percent error, match units, handle zero-value limits, and avoid lab-report mistakes.
- How to use the Half-Life CalculatorLearn how to calculate remaining amount, elapsed time, and half-life with matching units, examples, privacy notes, and safety limits.
- How to use the Exponent CalculatorLearn how to calculate powers, negative and zero exponents, decimal and fraction exponents, scientific notation, 0^0 limits, and common exponent mistakes.
Browse all 61 guides in this category
- How to use the Log CalculatorLearn custom-base logs, ln, log10, change-of-base steps, valid input rules, negative log answers, exponent checks, and common mistakes.
- How to use the Root CalculatorLearn square roots, cube roots, nth roots, decimal radicands, exponent form, power checks, negative-root limits, and common mistakes.
- Absolute Value Calculator GuideLearn absolute value, distance from zero, signed difference, absolute difference, number-line examples, and common mistakes.
- How to use the Quadratic Formula CalculatorLearn coefficient signs, standard form, discriminants, real roots, repeated roots, complex roots, graph details, and answer checks.
- How to use the Binary CalculatorLearn how to add, subtract, multiply, divide, and convert binary numbers with base-2 place values, decimal checks, and remainders.
- How to use the Hex CalculatorLearn hex arithmetic, bitwise AND, OR, and XOR, conversions, remainders, bit masks, and signed-value limits.
- How to use the Kawaii CalculatorLearn when to use the cute pastel calculator, how its buttons and shortcuts work, and how to keep recent calculations private in the browser.
- How to use the Scientific CalculatorLearn DEG/RAD mode, typed expressions, trig functions, logs, roots, powers, constants, history, and when this tool is useful.
- How to use a Fraction Calculator with stepsCalculate, simplify, compare, and convert fractions, mixed numbers, whole numbers, and terminating decimals with exact steps.
- LCM Calculator GuideLearn how to find the least common multiple of two or more whole numbers, read the steps, and use LCM for fractions and schedules.
- GCF Calculator GuideLearn how to find the greatest common factor, compare GCF with LCM, simplify fractions, and read exact integer steps.
- How to use the Factor CalculatorLearn how to list factors, factor pairs, prime factors, and prime factorization for positive whole numbers.
- How to use the Prime Factorization CalculatorLearn how to read prime factors, exponent form, factor trees, special cases like 1, and GCF or LCM checks.
- How to use the Long Division CalculatorLearn how quotient, remainder, decimal form, and the multiplication check work in whole-number long division.
- How to use the Rounding CalculatorLearn how to round by decimal places, significant figures, and place value using nearest, up, down, and truncate methods.
- Matrix Calculator GuideCheck 2x2 and 3x3 matrix addition, multiplication, transpose, and determinant steps with plain examples.
- How to use the Scientific Notation CalculatorLearn how to convert standard numbers to scientific notation and convert coefficient-times-power-of-10 form back to standard form.
- Why BigInt Keeps Huge Integer Math ExactLearn why normal numbers round past the safe-integer limit and how BigInt keeps exact digits, quotients, and remainders.
- How to use the Standard Deviation CalculatorLearn how to calculate sample or population standard deviation, variance, mean, count, formula steps, examples, and practical limits from one data set.
- How to use the Number Sequence CalculatorLearn how to generate arithmetic, geometric, and Fibonacci-style sequences, read formulas, check term limits, and avoid common pattern mistakes.
- How to use the Sample Size CalculatorLearn how to estimate completed survey responses with confidence level, margin of error, population proportion, finite population correction, and response-rate planning.
- How to use the Probability CalculatorLearn how to read P(A or B), P(A and B), complements, independent-event overlap, impossible inputs, and probability limits.
- How to use the Statistics CalculatorLearn how to read count, sum, mean, median, mode, range, quartiles, IQR, variance, and sample or population standard deviation.
- How to use the Average CalculatorLearn how to find the arithmetic mean, check the sum and count, and compare average with median, mode, and range.
- Mean, Median, Mode, Range Calculator GuideLearn how to enter a data set, check mean, median, mode, and range formulas, and spot outliers, ties, and no-mode cases.
- Permutation and Combination GuideLearn when to use nPr or nCr, how order changes counting, how no-replacement formulas work, and how to read exact examples.
- How to use the Z-score CalculatorLearn how to standardize a value, read above-or-below-average direction, and estimate a normal percentile.
- How to use the P-value CalculatorLearn how to choose the tail, enter a z-score, read standard-normal p-values, and avoid common interpretation mistakes.
- How to use the Confidence Interval CalculatorLearn how to calculate z confidence intervals for a mean or proportion with margin of error and clear formula steps.
- Can Three Sides Form a Triangle? SSS GuideCheck the triangle inequality, find a possible third-side range, and work through valid and invalid three-side examples.
- How to use the Volume CalculatorLearn how to use cubic units for boxes, cylinders, spheres, and cones, plus radius mistakes and conversion limits.
- How to use the Slope CalculatorLearn how to find slope from two points, read rise over run, spot vertical and horizontal lines, and check line equation mistakes.
- How to use the Area CalculatorLearn how to calculate flat-shape area, keep square units straight, and avoid radius, height, and odd-shape mistakes.
- Distance Formula Between Two PointsLearn how to substitute two coordinate points, check distance squared, keep an exact square root, and avoid route-distance mistakes.
- How to use the Circle CalculatorLearn how to find radius, diameter, circumference, and area from one known circle measurement.
- How to use the Surface Area CalculatorLearn how to calculate surface area for boxes, cubes, cylinders, spheres, and cones, avoid radius mistakes, and read square-unit material estimates.
- How to use the Pythagorean Theorem CalculatorLearn how to find the hypotenuse, solve a missing leg, use decimals and units, and avoid impossible right-triangle inputs.
- How to use the Right Triangle CalculatorLearn how to solve a right triangle from two sides, read area, perimeter, angles, and avoid impossible hypotenuse inputs.
- Square Footage Calculator GuideUse the Square Footage Calculator guide to measure rooms, walls, panels, gardens, and repeated rectangles, with inch conversion and material-waste checks.
- How to use the Density CalculatorUse the Density Calculator guide to divide mass by volume, label g/mL or kg/m3 results, check examples, and avoid unit-matching mistakes.
- How to use the Mass CalculatorLearn how density multiplied by volume gives mass and why matching units matter. Includes input tips, examples, result checks, and unit or mode notes for th...
- How to use the Weight CalculatorUse the physics Weight Calculator for mass times gravity, not BMI or ideal body weight. Includes input tips, examples, result checks, and unit or mode notes...
- How to use the Speed CalculatorUse the Speed Calculator guide for distance and elapsed time. Learn mph, km/h, m/s, decimal hours, stopped-time choices, and metric-distance checks.
- Voltage Drop Calculator GuideUse the Voltage Drop guide to estimate volts lost, percent drop, and load voltage, then avoid one-way length, low-voltage, and wire-sizing mistakes.
- Watts to Amps: 12 V, 120 V, 240 V and 3-PhaseLearn watts-to-amps formulas for 12 V DC, 120 V and 240 V AC, and line-to-line three-phase power, with milliamps, examples, and safety limits.
- Amps to Watts GuideUse the Amps to Watts guide to convert amps, volts, phase, and power factor into watts and kW, then avoid breaker and wire-sizing mistakes.
- Kilowatts to Amps GuideUse the Kilowatts to Amps guide to convert kW, volts, phase, power factor, and efficiency into amps, then avoid motor and wiring-sizing mistakes.
- kVA to Amps GuideUse the kVA to Amps guide to convert kVA and volts into amps for single-phase or three-phase systems, then avoid kW and voltage mistakes.
- Amp Hours to Watt Hours GuideUse the Amp Hours to Watt Hours guide to convert Ah and nominal volts into Wh and kWh, check a 12.8 V example, and avoid battery-energy mistakes.
- How to use the Watt Hours to Amp Hours CalculatorUse the Watt Hours to Amp Hours Calculator guide to convert Wh to Ah with nominal voltage, 12.8 V, 24 V, 48 V, and 120 V examples, and battery runtime cautions.
- How to use the Wire Resistance CalculatorLearn how copper AWG size and wire length affect estimated resistance. Includes input tips, examples, result checks, and unit or mode notes for the Wire Res...
- How to use the Wire Size CalculatorUse the Wire Size Calculator guide to estimate copper AWG size from amps, one-way length, voltage, phase, and voltage-drop target with practical examples.
- How to use the Stair CalculatorLearn how total rise turns into risers, treads, run, and stair angle. Includes input tips, examples, result checks, and unit or mode notes for the Stair Cal...
- Resistor Color Code Calculator GuideUse the Resistor Calculator guide to decode 4-band resistor color codes into ohms and tolerance, with 1 kOhm, 4.7 kOhm, gold, silver, and multimeter checks.
- Ohm's Law Calculator GuideUse the Ohm's Law Calculator guide to solve voltage, current, resistance, and power from two known values, then avoid unit and circuit-safety mistakes.