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Calculators that show their working

Get the answer, the formula behind it, and a worked example you can check by hand. Every calculation runs in your browser.

Most used calculators

The ones people reach for every day.

Percentage CalculatorA percentage of a number, or what percent one is of another.Loan CalculatorRepayment amounts for any fixed-rate loan.Mortgage CalculatorMonthly repayments, total interest and a full amortisation schedule.Compound Interest CalculatorSee how savings grow with compounding at any frequency.Tip CalculatorTip amount and per-person split for any bill.Calorie CalculatorDaily calories for your goal, activity level and body stats.BMI CalculatorBody mass index with WHO category bands, in metric or imperial.Date CalculatorDays, months and years between two dates.Age CalculatorWork out your exact age in years, months, days and seconds.

Browse by category

Every area that is live today — more open up as each calculator ships.

MathPercentages, fractions, geometry, algebra and number bases.FinanceLoans, mortgages, interest, tax and investment returns.PhysicsMotion, forces, electricity, thermodynamics and optics.Health & FitnessBMI, calories, body fat, heart rate and nutrition targets.StatisticsAverages, standard deviation, probability and grade curves.Date & TimeAge, date differences, durations, time zones and conversions.ConstructionConcrete, gravel, mulch, paint, tile and square footage.BiologyGenetics, populations, microbiology and animal dosing.SportsPace, splits, running and cycling performance metrics.ChemistryMolarity, dilutions, reactions and stoichiometry.Food & CookingRecipe scaling, baking ratios, cooking conversions.ElectronicsOhm's law, resistors, wire gauge, batteries and signals.AutomotiveFuel cost, gas mileage and trip planning.OtherBra sizing and random password generation.

Why CalcMax

Three things a generated answer box cannot do.

Shows the working

Every page carries the formula, at least two worked examples you can follow by hand, and a plain statement of what the result cannot tell you.

Solve for any variable

Know the answer but not the input? Enter a target BMI, monthly payment or race pace and work backwards to the numbers that get you there.

Private by design

The maths runs in your browser, not on our servers. Your salary, weight and dates never leave your device.

546 calculators