DocomintCalculators
58 free calculators covering math, finance, health, and dates — every calculation runs in your browser, so the numbers you enter are never sent to our servers.
Math tools cover everyday arithmetic and homework — percentages, fractions, ratios, and geometry — plus a full scientific calculator and unit converter. Finance tools handle loans, interest, tax, and budgeting math like EMI, mortgage payments, and compound interest. Health tools estimate BMI, calorie needs, and other body-composition figures using standard published formulas (Mifflin-St Jeor, the US Navy method, and others — each tool's page names the exact one it uses). Date tools handle age, date arithmetic, time zones, and calendar lookups.
No account is required for any of them, and every calculator here computes its result with plain JavaScript running on your device — there's no upload step, so nothing you type into a field is sent anywhere before you see the answer.
Featured Calculators
- Percentage CalculatorFind X% of a number, calculate percentage change, or work out what percent one number is of another.
- Fraction CalculatorSimplify a fraction or add, subtract, multiply, and divide two fractions, with the steps shown.
- Scientific CalculatorEvaluate math expressions with trig functions, logarithms, exponents, and parentheses — free online.
- Unit ConverterConvert length, weight, temperature, volume, area, and speed between metric and imperial units.
- GPA CalculatorCalculate your grade point average from a list of courses, grades, and credit hours.
- Average (Mean) CalculatorCalculate the mean, sum, count, and range of a list of numbers, instantly in your browser.
- Median CalculatorFind the middle value of a list of numbers — the median, unaffected by outliers.
- Standard Deviation CalculatorCalculate sample and population standard deviation and variance for a set of numbers.
- Ratio CalculatorSimplify a ratio to its lowest terms, or scale it up to match a target value.
- Prime Number CheckerCheck whether a number is prime, and see its smallest factor if it isn't.
- Factorial CalculatorCalculate N! (N factorial) — the product of every whole number from 1 up to N.
- LCM / GCD CalculatorFind the least common multiple and greatest common divisor of two or more numbers.
- Quadratic Equation SolverSolve ax² + bx + c = 0 for x, including complex roots when the discriminant is negative.
- Random Number GeneratorGenerate random whole numbers in a range, with or without repeats, using cryptographic randomness.
- Number Base ConverterConvert numbers between binary, octal, decimal, hexadecimal, or any base from 2 to 36.
- Triangle CalculatorCalculate a triangle's area, perimeter, and all three angles from its three side lengths.
- Circle CalculatorCalculate a circle's radius, diameter, circumference, and area from any one known value.
- Slope & Distance CalculatorCalculate the slope, distance, and midpoint between two points on a coordinate plane.
- EMI CalculatorCalculate the monthly EMI on a loan from its principal, interest rate, and term in months.
- VAT CalculatorAdd VAT to a net price or remove it from a VAT-inclusive price, at any rate.
- GST CalculatorAdd GST to a price or remove it from a GST-inclusive price, at any rate.
- Loan CalculatorCalculate a loan's monthly payment, total interest, and total cost from its term in years.
- Currency ConverterConvert between 20 major currencies using live, daily-updated exchange rates.
- Compound Interest CalculatorCalculate the future value of an investment with interest compounding daily to annually.
How to choose a Calculator
- Start from the category filters (Math, Finance, Health, Date) above if you know roughly what kind of calculation you need.
- For finance and health calculators, check that calculator's page for the exact formula and assumptions it uses — results are estimates based on standard formulas, not personalized advice.
- A few related calculations often go together — see the "Explore related calculations" chains below for common sequences like pricing a sale or tracking fitness.
- Every calculator page explains its formula, shows a worked example, and lists common mistakes people make with that specific calculation — worth a skim if the result looks off.