Mondo Knows Tools
228 Free Online Calculators for Finance, Health, Math & Everyday Use
Every calculator Mondo knows, sorted onto four shelves: money and finance, health and fitness, math, and everyday tech. Pick a shelf, or search the whole library. Each tool gives an instant answer, shows the formula it used, and runs entirely in your browser with nothing stored.
Money & FinanceLoans, savings, pay, tax and the cost of things.Health & FitnessBody, food, training and the numbers behind them.MathPercentages, statistics, geometry and quick algebra.Everyday & TechDates, home projects, cars, weather and unit conversions.Randomizers & PickersShuffles, draws, team picks, dice odds and decision makers.Unit ConvertersLength, weight, volume, area, speed, pressure, energy, power and data.
Where most people start
The four tools Mondo gets asked for first.
Mortgage CalculatorMonthly payment on a home loan, including tax, insurance, HOA and PMI.đ° Money & FinanceBMI CalculatorBody mass index with a healthy-range read-out.đŋ Health & FitnessPercentage CalculatorEvery common percentage question in one place.â MathLoan CalculatorPayment, total interest and total cost for any fixed-rate loan.đ° Money & Finance
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Type what you need, or filter by shelf. 228 tools, no dead ends.
228 calculators
Mortgage CalculatorMonthly payment on a home loan, including tax, insurance, HOA and PMI.đ° Money & FinanceLoan CalculatorPayment, total interest and total cost for any fixed-rate loan.đ° Money & FinanceAuto Loan CalculatorMonthly car payment with trade-in, down payment and sales tax.đ° Money & FinancePersonal Loan CalculatorMonthly payment and cost of an unsecured personal loan.đ° Money & FinanceStudent Loan CalculatorPayment and total interest on a student loan.đ° Money & FinanceBusiness Loan CalculatorPayment on a fixed-rate business loan.đ° Money & FinanceBoat Loan CalculatorMonthly payment on a boat or marine loan.đ° Money & FinanceHome Equity Loan CalculatorPayment on a fixed-rate home equity loan.đ° Money & FinanceRepayment CalculatorWhat it takes to repay a fixed balance at a given rate.đ° Money & FinanceAuto Loan with TaxCar payment with trade-in, down payment and sales tax rolled in.đ° Money & FinanceAmortization CalculatorSee how each payment splits between interest and principal.đ° Money & FinancePayment CalculatorSolve for the monthly payment on any loan.đ° Money & FinanceInterest CalculatorSimple or compound interest on a balance.đ° Money & FinanceSimple Interest CalculatorInterest that never compounds, straight from the formula I = P r t.đ° Money & FinanceCompound Interest CalculatorGrowth with compounding and optional regular deposits.đ° Money & FinanceSavings CalculatorHow a savings balance grows with regular deposits.đ° Money & FinanceCD CalculatorCertificate of deposit growth to maturity.đ° Money & FinanceInflation CalculatorWhat money is worth later, and what later money is worth now.đ° Money & FinanceInvestment CalculatorProjected value of an investment with regular contributions.đ° Money & FinanceRetirement CalculatorProjected nest egg and the income it could support.đ° Money & Finance401(k) CalculatorBalance at retirement with your contributions and employer match.đ° Money & FinanceIRA CalculatorGrowth of a traditional or Roth IRA with yearly contributions.đ° Money & FinanceRoth IRA CalculatorRoth growth and what the tax-free withdrawals could be worth.đ° Money & FinanceAnnuity CalculatorFuture value of a series of level payments.đ° Money & FinanceAnnuity Payout CalculatorTurn a lump sum into a steady monthly income.đ° Money & FinanceBond CalculatorPrice a bond from its coupon, term and market yield.đ° Money & FinanceMutual Fund CalculatorSee the drag that fund fees put on long-term growth.đ° Money & FinanceSalary CalculatorConvert between hourly, weekly, monthly and yearly pay.đ° Money & FinanceTake-Home Pay CalculatorEstimate net pay after federal tax, FICA and retirement.đ° Money & FinanceIncome Tax CalculatorUS federal income tax from the 2025 brackets.đ° Money & FinanceEstate Tax CalculatorFederal estate tax on a large estate.đ° Money & FinanceMarriage Tax CalculatorThe marriage bonus or penalty on two incomes.đ° Money & FinanceSales Tax CalculatorAdd sales tax to a price, or work backwards to the pre-tax price.đ° Money & FinanceVAT CalculatorAdd or remove value added tax.đ° Money & FinanceDiscount CalculatorSale price and savings from a percentage off.đ° Money & FinanceAPR CalculatorThe true annual cost of a loan once fees are included.đ° Money & FinanceAuto Lease CalculatorMonthly lease payment from cap cost, residual and money factor.đ° Money & FinanceLease CalculatorGeneric lease payment estimate.đ° Money & FinanceBudget CalculatorSee what is left each month, and how it lines up with 50/30/20.đ° Money & FinanceCommission CalculatorCommission on a sale, with an optional base salary.đ° Money & FinanceCredit Card Payoff CalculatorHow long a balance takes to clear, and what the interest costs.đ° Money & FinanceCredit Card Minimum Payment CalculatorThe real cost of paying only the minimum each month.đ° Money & FinanceDebt Consolidation CalculatorCompare your current debts with a single consolidated loan.đ° Money & FinanceDebt Payoff CalculatorPayoff time when you fix your payment above the interest.đ° Money & FinanceDebt-to-Income Ratio CalculatorThe ratio lenders look at before saying yes.đ° Money & FinanceDepreciation CalculatorStraight-line or declining-balance depreciation.đ° Money & FinanceDown Payment CalculatorHow much to put down, and how PMI changes with it.đ° Money & FinanceFHA Loan CalculatorFHA payment with its low down payment and mortgage insurance.đ° Money & FinanceVA Mortgage CalculatorVA loan payment including the funding fee.đ° Money & FinanceHELOC CalculatorHow much you could borrow against your home equity.đ° Money & FinanceHouse Affordability CalculatorThe home price that fits your income and debts.đ° Money & FinanceIRR CalculatorInternal rate of return from a series of cash flows.đ° Money & FinanceMargin CalculatorGross margin, markup and profit from cost and revenue.đ° Money & FinanceMortgage Payoff CalculatorHow extra payments shorten a mortgage and cut interest.đ° Money & FinancePayback Period CalculatorHow long until an investment pays for itself.đ° Money & FinancePension CalculatorDefined-benefit pension from salary, service and multiplier.đ° Money & FinancePresent Value CalculatorWhat a future sum is worth today.đ° Money & FinanceFuture Value CalculatorWhat today's money becomes at a given rate.đ° Money & FinanceRefinance CalculatorMonthly savings and break-even on a refinance.đ° Money & FinanceRent CalculatorRent as a share of income, against the 30% rule.đ° Money & FinanceRent vs Buy CalculatorA simple long-run comparison of renting and buying.đ° Money & FinanceRental Property CalculatorCap rate and cash flow for a rental.đ° Money & FinanceReal Estate CalculatorQuick return check on a property purchase.đ° Money & FinanceRMD CalculatorRequired minimum distribution from a retirement account.đ° Money & FinanceROI CalculatorReturn on investment, with an optional annualised figure.đ° Money & FinanceAverage Return CalculatorArithmetic vs geometric average of a series of returns.đ° Money & FinanceCash Back vs Low Interest CalculatorIs a rebate better than a lower rate?đ° Money & FinanceCollege Cost CalculatorWhat college could cost by the time you get there.đ° Money & FinanceSocial Security CalculatorRough estimate of a US retirement benefit from your earnings.đ° Money & FinanceCurrency ConverterConvert with live mid-market rates, or type the rate your bank quoted.đ° Money & FinanceFinance CalculatorSolve for any single unknown in a loan or savings formula.đ° Money & FinanceInterest Rate CalculatorFind the rate hiding in a loan's payment and term.đ° Money & FinancePaycheck by StateWhat actually lands in your account, state by state, after tax and FICA.đ° Money & FinanceCost of Living ComparisonWhat a salary in one city is worth in another.đ° Money & FinanceBMI CalculatorBody mass index with a healthy-range read-out.đŋ Health & FitnessBMR CalculatorBasal metabolic rate, the calories you burn at rest.đŋ Health & FitnessTDEE CalculatorTotal daily energy expenditure from your activity level.đŋ Health & FitnessCalorie CalculatorDaily calories for losing, keeping or gaining weight.đŋ Health & FitnessBody Fat CalculatorBody fat percentage from simple tape measurements.đŋ Health & FitnessArmy Body Fat CalculatorUS Army standard tape method for body fat.đŋ Health & FitnessLean Body Mass CalculatorHow much of your weight is lean tissue.đŋ Health & FitnessIdeal Weight CalculatorTarget weight ranges from the common clinical formulas.đŋ Health & FitnessHealthy Weight CalculatorThe weight range that keeps your BMI in the healthy band.đŋ Health & FitnessBody Surface Area CalculatorBSA from the Du Bois and Mosteller formulas.đŋ Health & FitnessMacro CalculatorSplit your calories into protein, carbs and fat, then into meals.đŋ Health & FitnessProtein CalculatorDaily protein target based on weight and training.đŋ Health & FitnessCarbohydrate CalculatorHow many carbs fit your calories and goal.đŋ Health & FitnessFat Intake CalculatorDaily fat grams from calories and share.đŋ Health & FitnessCalories Burned CalculatorEnergy burned in an activity, using MET values.đŋ Health & FitnessOne Rep Max CalculatorEstimate your 1RM from a set you have already done.đŋ Health & FitnessPace CalculatorPace, speed and finish time for a run or ride.đŋ Health & FitnessTarget Heart Rate CalculatorTraining zones from your age and resting pulse.đŋ Health & FitnessBlood Alcohol CalculatorEstimated blood alcohol content (Widmark formula).đŋ Health & FitnessGFR CalculatorEstimated kidney filtration rate (CKD-EPI 2021).đŋ Health & FitnessDue Date CalculatorEstimated due date from your last period.đŋ Health & FitnessPregnancy CalculatorHow far along you are and the milestones ahead.đŋ Health & FitnessConception CalculatorLikely conception window from your dates.đŋ Health & FitnessOvulation CalculatorOvulation day and the fertile window.đŋ Health & FitnessPeriod CalculatorYour next few period start dates.đŋ Health & FitnessPregnancy Weight Gain CalculatorThe recommended weight-gain range for your pregnancy.đŋ Health & FitnessBody Type CalculatorSomatotype read from your measurements.đŋ Health & FitnessBra Size CalculatorBand and cup size from two measurements.đŋ Health & FitnessVO2 Max EstimateEstimate your aerobic capacity from a test, your resting heart rate, or a brisk walk.đŋ Health & FitnessPercentage CalculatorEvery common percentage question in one place.â MathAverage CalculatorMean, median, mode and range of any list.â MathMean, Median, Mode, Range CalculatorThe four classic summaries, side by side.â MathStandard Deviation CalculatorSpread of a data set, population and sample.â MathStatistics CalculatorA full summary of a data set in one pass.â MathRandom Number GeneratorFair random numbers in any range.â MathRatio CalculatorSolve a proportion and simplify ratios.â MathPercent Error CalculatorHow far an estimate sits from the true value.â MathExponent CalculatorPowers and roots, including fractional exponents.â MathRoot CalculatorSquare roots, cube roots and any nth root.â MathLog CalculatorLogarithms in any base, natural and common.â MathBinary CalculatorConvert between binary and decimal.â MathHex CalculatorConvert between hexadecimal and decimal.â MathBig Number CalculatorMultiply or add very large integers exactly.â MathHalf-Life CalculatorRadioactive decay, or anything that halves.â MathQuadratic Formula CalculatorRoots of ax^2 + bx + c = 0, including complex ones.â MathSlope CalculatorSlope, line equation and angle between two points.â MathDistance CalculatorStraight-line distance between two points.â MathPythagorean Theorem CalculatorSolve a right triangle's missing side.â MathRight Triangle CalculatorEvery side and angle of a right triangle.â MathTriangle CalculatorArea and perimeter from three sides.â MathArea CalculatorArea of the common shapes.â MathCircle CalculatorRadius, diameter, circumference and area together.â MathSurface Area CalculatorSurface area of common 3D shapes.â MathVolume CalculatorVolume of the common solids.â MathFactor CalculatorAll divisors of a number and its prime factors.â MathGreatest Common Factor CalculatorThe largest number that divides a list exactly.â MathLeast Common Multiple CalculatorThe smallest number a list all divides into.â MathNumber Sequence CalculatorFind the next terms of an arithmetic or geometric sequence.â MathPermutation and Combination CalculatorWays to arrange or choose from a set.â MathProbability CalculatorTwo independent events, together or either.â MathConfidence Interval CalculatorRange that likely contains the true mean.â MathSample Size CalculatorHow many responses a survey needs.â MathScientific Notation CalculatorConvert to and from scientific notation.â MathRounding CalculatorRound to any precision, or to whole numbers.â MathZ-Score CalculatorHow many standard deviations a value sits from the mean.â MathFraction CalculatorAdd, subtract, multiply and divide fractions.â MathMatrix CalculatorMultiply, add, invert and take determinants of matrices you type in.â MathEquation SolverLinear, quadratic and two-variable systems, solved step by step.â MathPrime Number CheckerTest a number, factor it, or list the primes in a range.â MathAge CalculatorYour exact age in years, months and days.đ§ Everyday & TechDate CalculatorAdd or subtract days, weeks, months and years from a date.đ§ Everyday & TechDay CounterDays between two dates, in every unit that matters.đ§ Everyday & TechDay of the Week CalculatorWhich weekday any date falls on.đ§ Everyday & TechHours CalculatorHours worked between a start and end time.đ§ Everyday & TechTime Card CalculatorWeekly hours and pay from a simple timesheet.đ§ Everyday & TechTime Duration CalculatorThe gap between two dates and times.đ§ Everyday & TechTip CalculatorTip and per-person total for a bill.đ§ Everyday & TechSleep CalculatorBest bedtimes, wake times, or how much sleep you owe yourself.đ§ Everyday & TechGPA CalculatorWeighted GPA from your grades and credit hours.đ§ Everyday & TechGrade CalculatorWhat you need on the final to hit your target grade.đ§ Everyday & TechSquare Footage CalculatorArea of a room or plot in square feet.đ§ Everyday & TechConcrete CalculatorCubic yards of concrete for a slab.đ§ Everyday & TechGravel CalculatorTons of gravel for a driveway or bed.đ§ Everyday & TechMulch CalculatorBags or cubic yards of mulch for a bed.đ§ Everyday & TechTile CalculatorHow many tiles a floor or wall needs.đ§ Everyday & TechRoofing CalculatorRoofing squares and bundles from your footprint.đ§ Everyday & TechStair CalculatorRise, run and step count for a staircase.đ§ Everyday & TechBTU CalculatorHeating or cooling capacity for a room.đ§ Everyday & TechElectricity Cost CalculatorWhat an appliance costs to run.đ§ Everyday & TechOhms Law CalculatorVoltage, current, resistance and power from any two.đ§ Everyday & TechResistor Color Code CalculatorRead a 4-band resistor, or find the bands for a value.đ§ Everyday & TechVoltage Drop CalculatorVoltage lost along a wire run.đ§ Everyday & TechHorsepower CalculatorHorsepower from torque and rpm, or from a quarter mile.đ§ Everyday & TechFuel Cost CalculatorWhat a trip costs in fuel.đ§ Everyday & TechGas Mileage CalculatorFuel economy from miles and gallons.đ§ Everyday & TechSpeed CalculatorSpeed from distance and time.đ§ Everyday & TechTire Size CalculatorCompare two tire sizes and the speedometer error.đ§ Everyday & TechWind Chill CalculatorHow cold the wind makes it feel.đ§ Everyday & TechHeat Index CalculatorHow hot it feels with humidity.đ§ Everyday & TechDew Point CalculatorThe temperature at which dew forms.đ§ Everyday & TechGolf Handicap CalculatorEstimated handicap index from recent rounds.đ§ Everyday & TechGDP CalculatorGross domestic product from its spending parts.đ§ Everyday & TechBandwidth CalculatorDownload time from file size and speed.đ§ Everyday & TechBase64 Encode / DecodeConvert text to and from Base64.đ§ Everyday & TechURL Encode / DecodePercent-encode or decode a URL or parameter.đ§ Everyday & TechRoman Numeral ConverterConvert between numbers and Roman numerals.đ§ Everyday & TechDensity CalculatorDensity, mass or volume, whichever is missing.đ§ Everyday & TechMolarity CalculatorMolar concentration from mass, molar mass and volume.đ§ Everyday & TechMolecular Weight CalculatorMolar mass from a chemical formula.đ§ Everyday & TechUnit ConverterLength, weight, volume, temperature and speed conversions.đ§ Everyday & TechHeight ConverterFeet and inches to centimetres, and back.đ§ Everyday & TechWeight ConverterPounds, kilograms, stones and ounces.đ§ Everyday & TechShoe Size ConverterConvert shoe sizes between US, UK, EU and cm.đ§ Everyday & TechIP Subnet CalculatorNetwork, broadcast and host range from an IPv4 CIDR.đ§ Everyday & TechPassword GeneratorStrong random passwords, generated in your browser.đ§ Everyday & TechDice RollerRoll dice for games and decisions.đ§ Everyday & TechLove CalculatorA bit of fun with two names.đ§ Everyday & TechTimezone Meeting PlannerFind a time that works in two cities, and see the overlap at a glance.đ§ Everyday & TechRecipe ScalerScale a recipe up or down and get the new amounts for every ingredient.đ§ Everyday & TechPaint Coverage CalculatorHow much paint a room needs, in litres, gallons and cans.đ§ Everyday & TechList RandomizerShuffle a list into a random order.đ˛ Randomizers & PickersRandom Name PickerFair way to pick one name, or several, from a group.đ˛ Randomizers & PickersRandom Team GeneratorSplit a list of players into evenly sized teams.đ˛ Randomizers & PickersRandom Choice GeneratorLet the coin decide between your options.đ˛ Randomizers & PickersWheel SpinnerA real spinning wheel with sound that picks your winner.đ˛ Randomizers & PickersRandom Letter GeneratorDraw random letters for word games and classrooms.đ˛ Randomizers & PickersRandom Color GeneratorGenerate random colours with hex and RGB values.đ˛ Randomizers & PickersRandom String GeneratorRandom letters, digits and symbols at any length.đ˛ Randomizers & PickersRandom Country GeneratorPick a random country from all 195.đ˛ Randomizers & PickersRandom State GeneratorPick a random US state.đ˛ Randomizers & PickersRandom Date GeneratorDraw a random date inside any range.đ˛ Randomizers & PickersRandom Month GeneratorPick a random month, with or without a year.đ˛ Randomizers & PickersLottery Number GeneratorDraw unique lottery numbers in sorted order.đ˛ Randomizers & PickersBingo Card GeneratorBuild a valid 75-ball bingo card in one click.đ˛ Randomizers & PickersSecret Santa GeneratorPair a group so nobody draws their own name.đ˛ Randomizers & PickersDiceware Passphrase GeneratorMemorable passphrases built from random words.đ˛ Randomizers & PickersDice Probability CalculatorExact odds of rolling a total on any number of dice.đ˛ Randomizers & PickersElo Rating CalculatorExpected score and rating change for a game of Elo.đ˛ Randomizers & PickersRandom Alphanumeric GeneratorGenerate random letters and digits in any mix.đ˛ Randomizers & PickersTournament Bracket GeneratorSeed single-elimination brackets with byes.đ˛ Randomizers & PickersPoker Odds CalculatorWork out your outs, and the odds of hitting them.đ˛ Randomizers & PickersTemperature ConverterConvert Celsius, Fahrenheit, Kelvin and Rankine.đ Unit ConvertersLength ConverterConvert metres, feet, miles, inches and more at once.đ Unit ConvertersWeight and Mass ConverterConvert kilograms, pounds, ounces, stones and tonnes.đ Unit ConvertersVolume ConverterConvert litres, gallons, cups, pints and millilitres.đ Unit ConvertersArea ConverterConvert square metres, square feet, acres and hectares.đ Unit ConvertersSpeed ConverterConvert mph, km/h, m/s, knots and feet per second.đ Unit ConvertersPressure ConverterConvert bar, psi, kPa, atm and mmHg.đ Unit ConvertersEnergy ConverterConvert joules, calories, kWh, BTU and food calories.đ Unit ConvertersPower ConverterConvert watts, horsepower, kW and BTU per hour.đ Unit ConvertersData Storage ConverterConvert bytes, KB, MB, GB, TB and binary units.đ Unit ConvertersCooking MeasurementsCups, tablespoons and millilitres, plus grams for the ingredient you are actually using.đ Unit ConvertersFuel Economy ConverterMPG, L/100 km and km per litre, plus what a trip actually costs.đ Unit ConvertersTorque and Force ConverterNewton-metres, pound-feet and kilogram-force, plus the force a wrench actually applies.đ Unit Converters
Questions people ask
- How many calculators and tools are there?
- 228 tools across 6 categories: money and finance, health and fitness, maths, everyday tech, randomisers and converters. Each one shows the formula it uses.
- Are the results reliable?
- The working is shown so you can check it, and money tools use published rates and brackets. They are estimates for guidance rather than financial, medical or legal advice.
- Is anything I type stored?
- No. Everything runs in your browser, so the figures never leave your device and there is no account to create. That also means a calculation keeps working offline once the page has loaded.