13 calculators
Math Calculators
The answer and every step to get there
These math calculators solve the problems that come up in class and in daily life, from percentages and fractions to quadratic equations and statistics, and show the steps so you can follow the method.
See all 13 calculatorsThe key idea
A calculator that only gives the answer does not teach the method
Knowing that 3/4 + 5/6 = 19/12 is useful; seeing that you need a common denominator of 12 is what lets you do the next one alone. Every math calculator here shows the formula and the steps.
What you can calculate
13 calculators, one for every question
Percentage Calculator
Percent of a number, percent off, increases and percent change.
Calculate 02Proportion Calculator
Direct or inverse, with the setup shown.
Calculate 03Fraction Calculator
Add, subtract, multiply and divide fractions step by step.
Calculate 04GCF and LCM Calculator
Greatest common factor and least common multiple, with prime factors.
Calculate 05Quadratic Equation Calculator
Roots of ax² + bx + c = 0, discriminant and vertex.
Calculate 06System of Equations Calculator (2×2)
Two equations, two unknowns. Solved in seconds.
Calculate 07Statistics Calculator: Mean, Median and Mode
Paste your data: mean, median, mode and standard deviation.
Calculate 08Permutation and Combination Calculator
How many ways to choose? With or without order and repetition.
Calculate 09Pythagorean Theorem Calculator
The hypotenuse or the missing leg, with area and perimeter.
Calculate 10Area Calculator
Area and perimeter of 11 shapes, L-shaped rooms included.
Calculate 11Unit Converter
Length, weight, volume, area and speed, US and metric.
Calculate 12Fahrenheit to Celsius Converter
Fahrenheit, Celsius and Kelvin in one tap.
Calculate 13Roman Numeral Converter
Numbers to Roman numerals and back, with the breakdown.
CalculateHow we work
How we build calculators, in three principles
Diagnosis
Source first
Every formula comes from the law, the agency or the original study.
If a calculation depends on a rule (federal tax brackets, the Fair Labor Standards Act, Social Security), we start from the official text from the IRS, the Department of Labor or the SSA and link it on the page. If it depends on a study, we cite the study.
No figures copied from another calculator.
Method
Checked by hand
Every calculator is tested against cases worked out by hand.
The example on each page is one of those cases and matches the tool to the cent. We also test the edge cases: zeros, negatives, legal caps and odd dates.
When a rule changes, we review it and log the change on our corrections page.
Tool
Built to be understood
The result comes with the formula, the example and the common questions.
Everything runs in your browser, instantly and with no sign-up. You can share a calculation with a link, save it to your history or download it to Excel.
We do not store what you type.
Common questions
Frequently asked questions
How do I calculate a percentage?
Multiply the number by the percentage and divide by 100: 20% of 150 is 150 × 20 / 100 = 30. The percentage calculator also does increases, decreases and percent change.
How do I add fractions?
Find a common denominator, convert both fractions and add the numerators: 3/4 + 5/6 = 9/12 + 10/12 = 19/12.
How do I solve a quadratic equation?
With the quadratic formula: x = (−b ± √(b² − 4ac)) / 2a. The discriminant b² − 4ac tells you whether there are two, one or no real solutions.
Are the unit conversions exact?
Yes: we use the exact definitions published by NIST, such as 1 inch = 2.54 cm and 1 pound = 0.45359237 kg.
Do the calculators show the steps?
Yes. Each page explains the formula, works through an example and shows the intermediate results where they help.
Is my data saved?
No. Everything is calculated in your browser.
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