Free online calculators

Finance, health, math and dates. Every calculator on this site runs in your browser, so results appear as you type and nothing you enter is uploaded anywhere.

Finance

Loans & Debt
Mortgage CalculatorEstimate your monthly mortgage payment and see what the loan really costs over its lifetime.
Loan CalculatorMonthly payment and total interest for any fixed-rate loan: personal, student, car or otherwise.
Auto Loan CalculatorYour real car payment, including sales tax, down payment and trade-in value.
Amortization CalculatorMonthly payment plus the full year-by-year schedule of principal, interest and balance.
Credit Card Payoff CalculatorHow long your balance takes to clear at a given payment, and what the interest costs you.
Savings & Investing
Compound Interest CalculatorSee how money grows when interest earns interest, with or without monthly contributions.
Simple Interest CalculatorInterest computed on the principal only. The I = Prt formula from class, done instantly.
Retirement CalculatorWhat your savings grow to by retirement, and the monthly income they could support.
Inflation CalculatorWhat inflation does to your money: future prices, and what today's cash will still buy.
ROI CalculatorTotal return on an investment, and the annualized rate if you enter how long you held it.
CAGR CalculatorThe smoothed annual growth rate that turns your starting value into the ending one.
APY CalculatorWhat a nominal rate really yields once compounding is counted.
Income & Tax
Salary CalculatorEnter your pay in any period and get hourly to annual and everything in between, converted instantly.
Sales Tax CalculatorAdd tax to a price, or work backwards from a receipt total to the pre-tax price.
VAT CalculatorAdd VAT to a net price, or pull the VAT back out of a gross amount.
Everyday Money
Tip CalculatorTip amount, total, and everyone's share. Fast enough to settle it at the table.
Discount CalculatorSale price, amount saved, and what an 'extra 20% off' on top really means.
Business
Margin CalculatorGross margin and markup from cost and price, or the price that hits a target margin.
Markup CalculatorSelling price from cost and markup, or the markup a price implies.
Break-Even CalculatorHow many units you must sell before the fixed costs are covered.

Construction

Concrete CalculatorHow much concrete your slab needs, as volume and as bags of premix.
Stair CalculatorSteps, riser height, total run and stringer length from the floor-to-floor rise.
Roof Pitch CalculatorRise and run in, standard x/12 pitch, angle and rafter multiplier out.
Wall Stud CalculatorStud count for a wall at 16 or 24 inch spacing, plus the plate lumber.
Drywall CalculatorSheet count for a room, walls and ceiling, with the waste allowance under your control.
Gravel CalculatorGravel for an area, as volume and as the weight you order it by.
Board Foot CalculatorBoard feet for a lumber order, and the cost at a price per board foot.

Home

Paint CalculatorHow much paint the room actually needs, with doors, windows and coats accounted for.
Square Footage & Area CalculatorArea from length and width, in feet or meters, with cost per unit area if you need it.
Mulch CalculatorMulch for a bed, as volume and as bags.
Tile CalculatorTile count for a floor or wall, waste included, plus boxes to buy.
Wallpaper CalculatorHow many rolls the room needs, from the wall size, roll size and pattern repeat.
Flooring CalculatorFlooring to buy for a room, with waste, boxes and cost.
Brick CalculatorBricks for a single-layer wall, from the wall size, brick size and mortar joint.
Paver CalculatorPavers for a patio or walkway, plus the bedding sand under them.
BTU CalculatorThe air conditioner capacity a room needs, in BTU, tons and kilowatts.

Electrical

Ohm's Law CalculatorAny two of volts, amps, ohms and watts in, all four out.
Watts to Amps CalculatorWatts to amps at any voltage, and back.
kW to Amps CalculatorKilowatts to amps at any voltage, for DC, single-phase and three-phase circuits.
kVA to Amps CalculatorkVA to amps for single-phase and three-phase circuits. No power factor needed.
kVA to kW CalculatorkVA to kW and back. The only ingredient is the power factor.
kW to kVA CalculatorHow many kVA a load of a given kW needs, from the power factor.
HP to Amps CalculatorHow many amps a motor of a given horsepower draws, with efficiency and power factor included.
Voltage Divider CalculatorVout from Vin and two resistors, plus the current and wasted power.
Series & Parallel Resistor CalculatorTotal resistance of any set of resistors, in series and in parallel.
LED Resistor CalculatorThe series resistor your LED needs, with the nearest standard value and wattage.
Battery Life CalculatorRuntime from capacity and load, with a realistic derating built in.
Voltage Drop CalculatorWhat a cable run steals from your voltage, by wire size and length.
Electricity Cost CalculatorWhat any appliance costs to run, per day, month and year.

Health

BMI CalculatorYour body mass index, weight category, and the healthy weight range for your height.
Calorie CalculatorHow many calories you burn per day, and what to eat to maintain, lose, or gain weight.
BMR CalculatorThe calories your body burns at complete rest, the baseline every diet plan starts from.
Body Fat CalculatorBody fat percentage from tape measurements using the US Navy method. No calipers needed.
Ideal Weight CalculatorYour ideal body weight by four standard medical formulas, plus the healthy BMI range.
Pregnancy Due Date CalculatorYour estimated due date, how far along you are, and your current trimester.
TDEE CalculatorYour total daily energy expenditure, with every activity level shown so you can sanity-check the multiplier.
One Rep Max CalculatorYour estimated 1RM from any hard set, plus the training percentages built on it.
Pace CalculatorKnow two of pace, time and distance? Solve for the third, per kilometer or per mile.
Macro CalculatorYour daily calories split into grams of protein, carbs and fat.
Protein Intake CalculatorHow many grams of protein you need per day, from your weight and goal.
Water Intake CalculatorA daily water target from your body weight and training time.
Heart Rate Zone CalculatorYour five training zones, from age alone or sharpened with your resting heart rate.
Dog Age CalculatorYour dog's age in human years, adjusted for size, because small dogs age slower.
Cat Age CalculatorYour cat's age in human years, using the veterinary convention.
Sleep CalculatorBedtimes that fit whole 90-minute sleep cycles, so the alarm doesn't land mid-cycle.

Math

Numbers
Percentage CalculatorThe three percentage questions everyone actually asks, answered instantly.
Fraction CalculatorAdd, subtract, multiply or divide two fractions. Simplified, as a mixed number, and as a decimal.
GCD & LCM CalculatorGreatest common divisor and least common multiple of any list of whole numbers.
Exponent CalculatorAny base to any power, including negative and fractional exponents.
Root CalculatorSquare root, cube root, or any nth root.
Logarithm CalculatorThe logarithm of any number, in base 10, base 2, e, or a base of your choosing.
Percentage Increase CalculatorHow much a value grew, as a percentage of where it started.
Percentage Decrease CalculatorHow much a value fell, as a percentage of where it started.
Percentage Change CalculatorThe signed percent change from one value to another, up or down.
Percentage Difference CalculatorThe symmetric percent difference between two values, measured against their average.
Percent Error CalculatorHow far your measurement landed from the accepted value, in percent.
Ratio CalculatorSimplify a ratio to lowest terms, or solve A : B = C : D for the missing value.
Statistics & Probability
Average CalculatorPaste any list of numbers and get the mean, median, sum, spread and more.
Standard Deviation CalculatorSample and population standard deviation, variance and mean from any list of numbers.
Combinations & Permutations CalculatorHow many ways to choose r items from n (order ignored) or arrange them (order matters).
Probability CalculatorCombine two independent events, and see the odds over repeated tries.
Mean Median Mode CalculatorAll four centers of your data at once: mean, median, mode and range.
Variance CalculatorSample and population variance from any list of numbers, with the standard deviations alongside.
Z-Score CalculatorHow many standard deviations a value sits from the mean, and the percentile that implies.
Algebra
Quadratic Formula CalculatorSolve ax² + bx + c = 0. Real or complex roots, with the discriminant shown.
Arithmetic Sequence CalculatorThe nth term and the sum of the first n terms, from the first term and common difference.
Geometric Sequence Calculatornth term, sum of n terms, and the infinite sum when the ratio allows one.
Geometry
Pythagorean Theorem CalculatorFind the missing side of a right triangle, plus its angles, area and perimeter.
Right Triangle CalculatorGive it any two values and get every side, angle, the area and the perimeter.
Triangle Area CalculatorArea from base and height, or from three sides using Heron's formula.
Circle CalculatorEnter any one measurement of a circle and get all the others.
Rectangle CalculatorArea, perimeter and diagonal from length and width.
Trapezoid Area CalculatorArea from the two parallel sides and the height between them.
Regular Polygon CalculatorEverything about a regular polygon from its side count and side length.
Hexagon CalculatorArea, diagonals and apothem of a regular hexagon from one side.
Arc Length CalculatorArc length, sector area, chord and segment from radius and central angle.
Ellipse CalculatorArea, circumference and eccentricity from the two semi-axes.
Volume CalculatorVolume and surface area for the common solids.
Slope CalculatorTwo points in, everything about the line through them out.

Chemistry

Molarity CalculatorConcentration in mol/L from mass and volume, or the mass to weigh out for a target molarity.
Dilution CalculatorC₁V₁ = C₂V₂, solved for whichever value you're missing.
Half-Life CalculatorExponential decay, solved for the remaining amount, the half-life or the time.
Ideal Gas Law CalculatorPV = nRT, solved for whichever variable you're missing.

Physics

Motion
Acceleration CalculatorAcceleration from a change in velocity, plus g-force and distance covered.
Velocity CalculatorAverage velocity from distance and time, in every common unit.
Displacement CalculatorChange of position, sign and all.
Angular Velocity CalculatorRotation rate in rad/s, rpm and deg/s, plus rim speed at a radius.
Angular Acceleration CalculatorHow fast a rotation spins up or down.
Pendulum CalculatorSwing period from length, or the length for a target period.
Simple Harmonic Motion CalculatorWhere an oscillator is and how fast it moves, at any instant.
Forces
Force CalculatorNewton's second law, solved for whichever of F, m and a you're missing.
Weight CalculatorWhat a mass weighs, on Earth or anywhere else.
Friction CalculatorFriction force from the coefficient and normal force.
Tension CalculatorRope tension for a hanging mass, still or accelerating.
Torque CalculatorTurning force from force, lever arm and angle.
Gravitational Force CalculatorNewton's universal gravitation. Scientific notation like 5.97e24 works.
Spring Constant CalculatorHooke's law both ways, with the stored energy included.
Energy & Work
Work CalculatorWork from force, distance and the angle between them.
Kinetic Energy CalculatorThe energy of motion, from mass and velocity.
Potential Energy CalculatorStored energy of height, and the speed it turns into if dropped.
Mechanical Energy CalculatorKinetic plus potential: the total an object carries.
Strain Energy CalculatorEnergy stored in an elastically loaded part.
Specific Heat CalculatorThe heat needed to warm something up (or released cooling down).
Heat Capacity CalculatorHow much heat an object soaks up per degree.
Latent Heat CalculatorThe heat of melting and boiling, where temperature stands still.
Matter & Waves
Density CalculatorDensity from mass and volume, with the sink-or-float check against water.
Pressure CalculatorForce over area, or water pressure at depth.
Wavelength & Frequency CalculatorWavelength from frequency and back, for light, sound, or any wave speed.
Refractive Index CalculatorHow much a material slows light, both directions.
Intensity CalculatorPower spread over area, with the sound level in dB.
Shear Modulus CalculatorStiffness against sliding deformation, from a shear test's numbers.
Hubble's Law CalculatorHow fast the expansion carries a galaxy away, or how far it is.
Electricity & Fields
Faraday's Law CalculatorThe voltage a changing magnetic field induces in a coil.
Surface Charge Density CalculatorCharge spread over a surface. Scientific notation like 2e-6 works.
Energy Density CalculatorStored energy per volume.
Cell Potential CalculatorBattery voltage from the two half-reaction potentials.

Gamedev

3D Math
Vector CalculatorDot product, cross product, angle and magnitudes of two 3D vectors. Set z to 0 for 2D.
3D Distance CalculatorDistance, midpoint and direction between two points in 3D space.
Quaternion / Euler Angle ConverterEuler angles to quaternion and back, in degrees, convention stated.
Camera & Display
FOV CalculatorHorizontal to vertical FOV and back, for any aspect ratio.
Aspect Ratio CalculatorThe ratio of any resolution, and matching heights for a new width.
FPS to ms ConverterFPS to milliseconds and back, with the frame budget spelled out.

Dates

Age CalculatorYour exact age down to the day, total days lived, and how long until your next birthday.
Days Between Dates CalculatorThe exact number of days between two dates, plus weeks, weekdays, and a full breakdown.
Add or Subtract DaysWhat date is 90 days from today? Add or subtract any amount of time from any date.
Time CalculatorAdd or subtract two times in hours, minutes and seconds.
Time Duration CalculatorHow long between two clock times, including spans that cross midnight.
Business Days CalculatorCount working days between two dates, or add business days to find a deadline.
Week Number CalculatorThe ISO week number of any date, with the US convention and day-of-year alongside.

Everyday

GPA CalculatorYour grade point average on the 4.0 scale, from letter grades and credit hours.
Final Grade CalculatorThe score you need on the final exam to end up with the grade you want.
Fuel Cost CalculatorWhat the trip costs in fuel, from distance, economy and pump price.
Hours CalculatorHours between two clock times, minus the break, with decimal hours for the timesheet.
Speed Distance Time CalculatorKnow two of speed, distance and time? Solve for the third, in any units.
Weather
Wind Chill CalculatorWhat the cold actually feels like once the wind gets involved.
Heat Index CalculatorWhat the heat actually feels like once humidity blocks your sweat.
Dew Point CalculatorThe temperature air must cool to before its moisture condenses, and what that says about comfort.

Converters

Length ConverterMillimeters, Centimeters, Meters, Kilometers, Microns and more: 90 conversions
Weight ConverterMicrograms, Milligrams, Carats, Grains, Troy Ounces and more: 132 conversions
Temperature ConverterCelsius, Fahrenheit, Kelvin and more: 6 conversions
Area ConverterSquare Millimeters, Square Centimeters, Square Meters, Hectares, Square Kilometers and more: 90 conversions
Volume ConverterMilliliters, Deciliters, Liters, Cubic Meters, Teaspoons and more: 306 conversions
Speed ConverterKilometers per Hour, Miles per Hour, Meters per Second, Knots, Feet per Second and more: 30 conversions
Time ConverterNanoseconds, Milliseconds, Seconds, Minutes, Hours and more: 72 conversions
Data Storage ConverterBits, Bytes, Kilobytes, Megabytes, Gigabytes and more: 42 conversions
Pressure ConverterPascals, Kilopascals, Megapascals, Bar, PSI and more: 72 conversions
Energy ConverterJoules, Kilojoules, Megajoules, Calories, Kilocalories and more: 72 conversions
Power ConverterWatts, Kilowatts, Megawatts, Horsepower, BTU per Hour and more: 20 conversions
Fuel Economy ConverterLiters per 100 km, Kilometers per Liter, Miles per Gallon (US), Miles per Gallon (UK) and more: 12 conversions
Angle ConverterDegrees, Radians, Gradians, Arcminutes, Arcseconds and more: 20 conversions
Force ConverterNewtons, Kilonewtons, Pounds-force, Kilograms-force and more: 12 conversions
Frequency ConverterHertz, Kilohertz, Megahertz, Gigahertz, RPM and more: 20 conversions
Torque ConverterNewton-meters, Foot-pounds, Inch-pounds, Kilogram-centimeters and more: 12 conversions
Data Transfer Rate ConverterKilobits per Second, Megabits per Second, Gigabits per Second, Kilobytes per Second, Megabytes per Second and more: 30 conversions
Feet & Inches to cm ConverterFeet and inches to centimeters, or centimeters back to feet and inches.
Inch Fraction CalculatorTape-measure fractions to decimal and millimeters, or any measurement back to the nearest fraction.
Binary, Hex & Decimal ConverterConvert a number between binary, octal, decimal, hex, or any base up to 36.
Grams to Cups ConverterGrams to cups or cups to grams, with the right density for each ingredient.
Oven Temperature ConverterCelsius, fan oven, Fahrenheit and gas mark, converted the way cookbooks round them.
Cake Pan Size ConverterHow much to scale a recipe when your pan is a different size or shape.
Recipe ScalerTurn a recipe for 4 into a recipe for any number, one ingredient at a time.