Big questions. Clear answers.

Percentage

Find a percentage of any number.

Percentage change

Measure the increase or decrease between two values.

Fraction to decimal

Convert a fraction to a decimal and percentage.

Right triangle

Find the hypotenuse from two perpendicular sides.

Circle area

Find area and circumference from a radius.

Loan payment

Estimate monthly payments and total interest.

Car loan & payment by credit score

Estimate car payments with a dated credit-tier rate, trade-in, tax, and term comparisons.

Mortgage payment

Estimate a monthly home payment, compare extra payments, and see an amortization schedule.

Compound growth

Explore growth with monthly contributions.

Savings goal

Find a monthly contribution for your target.

Discount & sales tax

Calculate a discounted price with entered tax.

Debt payoff planner

Compare payoff dates and download a payment schedule.

Multi-debt payoff

Compare avalanche and snowball plans for several debts.

Room area

Estimate floor area and material allowance.

Concrete volume

Estimate cubic yards for a rectangular slab.

Paint coverage

Estimate gallons from area, coats, and coverage.

Miles to kilometers

Convert distances using the exact mile definition.

Kilograms to pounds

Convert metric mass to pounds.

Fahrenheit to Celsius

Convert a temperature between two scales.

Speed converter

Convert miles per hour to km/h and m/s.

Everyday

Tip & split bill

Split a bill and tip among a group.

Everyday

Road trip fuel cost

Estimate fuel spending for a journey.

Everyday

Hours to minutes

Convert decimal hours to hours and minutes.

Adult BMI

Calculate a body mass index from height and weight.

Square root

Find the principal square root of a nonnegative number.

Exponent

Raise a number to an integer or fractional power.

Logarithm

Calculate a logarithm for a chosen base.

Quadratic equation

Find the real roots of ax² + bx + c = 0.

Slope

Calculate the slope between two points.

Distance between points

Find straight-line distance in a two-dimensional plane.

Triangle area

Calculate area from base and perpendicular height.

Trapezoid area

Find area from two parallel sides and their separation.

Sphere volume

Calculate volume and surface area from a radius.

Cylinder volume

Find volume and total surface area of a closed cylinder.

Cone volume

Calculate the volume of a right circular cone.

Greatest common divisor

Find the largest integer divisor shared by two numbers.

Least common multiple

Find the smallest common positive multiple.

Factorial

Calculate n! for a nonnegative integer.

Combinations

Count unordered selections without replacement.

Arithmetic sequence

Find a term and partial sum of an arithmetic sequence.

Simple interest

Estimate interest without compounding.

Return on investment

Compare net proceeds with the amount invested.

Annualized growth rate

Find the constant annual growth rate between two values.

Profit margin

Measure profit as a percentage of revenue.

Markup pricing

Set a price from cost and a markup percentage.

Break-even sales

Estimate units needed to cover fixed and variable costs.

Hourly to annual salary

Convert hourly pay using your work schedule.

Emergency fund target

Calculate a reserve from your monthly expenses.

Debt-to-income ratio

Compare monthly debt payments with gross income.

Inflation adjustment

Estimate a future price at a constant assumed inflation rate.

Force

Apply Newton’s second law to mass and acceleration.

Kinetic energy

Calculate translational energy from mass and speed.

Gravitational potential energy

Estimate energy above a reference height.

Momentum

Calculate linear momentum for one object.

Mechanical work

Calculate work for a constant force and displacement.

Power from energy

Find average power over a time interval.

Ohm’s law

Calculate current through a resistance.

Electrical power

Calculate DC electrical power from voltage and current.

Pressure

Calculate pressure from force and contact area.

Density

Find density from mass and volume.

Wave speed

Relate frequency, wavelength, and propagation speed.

Frequency from period

Convert the time per cycle to frequency.

Average acceleration

Compare starting and final velocity over time.

Free-fall time

Estimate falling time from rest without air resistance.

Spring force

Apply Hooke’s law to a spring displacement.

Mean

Find the arithmetic mean of a list of numbers.

Median

Find the middle value in an ordered data set.

Standard deviation

Measure sample dispersion around the mean.

Sample variance

Calculate squared spread around the sample mean.

Range

Find the distance between smallest and largest values.

Z-score

Express an observation in standard-deviation units.

Standard error of mean

Estimate uncertainty in a sample mean.

Mean confidence interval

Build a normal-approximation interval with a chosen z value.

Event probability

Calculate probability for equally likely outcomes.

Weighted mean

Calculate an average using matching weights.

Centimeters to inches

Convert metric lengths to inches.

Feet to meters

Convert feet to meters.

Liters to US gallons

Convert volume using US liquid gallons.

Ounces to grams

Convert avoirdupois weight ounces to grams.

Celsius to kelvin

Convert temperature to the absolute scale.

Square feet to square meters

Convert area between customary and metric units.

Acres to hectares

Convert land area to hectares.

PSI to kilopascals

Convert pressure from psi to kPa.

Degrees to radians

Convert an angle to radians.

Kilojoules to food calories

Convert energy to nutritional kilocalories.

Tile quantity

Estimate tiles for a rectangular area.

Gravel quantity

Estimate aggregate volume and mass.

Mulch volume

Estimate mulch for garden beds.

Roof pitch

Convert rise and run to slope and angle.

Stair riser estimate

Divide a total rise into evenly sized risers.

Board feet

Calculate nominal lumber volume.

Wall area

Estimate wall surface after subtracting openings.

Waist-to-height ratio

Calculate a body measurement ratio without diagnosis.

Waist-to-hip ratio

Compare waist and hip measurements.

Body weight change

Track the percentage change between two measurements.

Running pace

Calculate time per kilometer from a run.

Race time estimate

Estimate finish time at a constant pace.

Cycling average speed

Find average speed over a ride.

Swimming pace

Find minutes per 100 meters.

Winning percentage

Measure wins as a share of games played.

Strength training volume

Calculate total external load across equal sets.

Recipe scaling

Scale an ingredient to a new serving count.

Baker’s percentage

Express ingredient weight relative to flour weight.

Dough hydration

Calculate water as a percentage of flour mass.

Recipe cost per serving

Divide a batch ingredient cost by portions.

Coffee brew ratio

Calculate water from coffee dose and chosen ratio.

Electricity cost

Estimate energy use and cost from appliance runtime.

Electricity emissions

Estimate emissions using your own grid factor.

Water use

Estimate consumption from flow rate and runtime.

Rainwater collection

Estimate roof runoff capture from a rainfall event.

Solar generation estimate

Model energy from array size and sunlight hours.

Moles from mass

Convert a substance’s mass to amount in moles.

Molarity

Find amount concentration in a solution.

Solution dilution

Calculate stock volume for a target concentration.

Ideal gas volume

Find gas volume from amount, temperature, and pressure.

Mass percent

Calculate solute mass as a share of solution mass.

Percent yield

Compare actual and theoretical product amounts.