Tools that do the working out
Free calculators and converters, with formulas you can understand.
150 resources
Air Changes per Hour Calculator
Calculate an ideal air-change rate from volume flow and room volume.
Acceleration Calculator
Find average acceleration from a velocity change and elapsed time.
Annulus Area Calculator
Find the area between two concentric circles.
Annual Percentage Yield Calculator
Convert a nominal annual rate to an effective annual yield with regular compounding.
Arc Length Calculator
Calculate a circular arc’s length from its radius and central angle.
Area Calculator
Calculate the area of a rectangle from its length and width.
Area Converter
Convert area measurements with clearly labeled units and instant results.
Arithmetic Mean Calculator
Calculate the arithmetic mean of three numeric values.
Arithmetic Sequence Calculator
Find an indexed term in an arithmetic sequence.
Aspect Ratio Calculator
Express an image or display’s width-to-height ratio as a decimal.
Binomial Probability Calculator
Find the probability of exactly k successes in independent equal-probability trials.
Battery Energy Calculator
Estimate nominal battery energy from volts and ampere-hours.
BMI Calculator
Calculate adult body mass index from weight and height.
Battery Runtime Calculator
Estimate operating time using usable watt-hours and a constant load.
Break-Even Calculator
Find the whole-unit sales volume needed to cover fixed and variable costs.
Buoyant Force Calculator
Calculate the upward force associated with displaced fluid.
Capacitor Energy Calculator
Calculate energy stored in an ideal capacitor.
Circle Calculator
Calculate circle area and circumference from its radius.
Combinations Calculator
Count unordered selections without replacement from distinct items.
Concrete Calculator
Estimate slab volume with an adjustable waste allowance.
Concrete Bag Quantity Calculator
Estimate bagged concrete quantities using the manufacturer’s mixed yield.
Compound Interest Calculator
Estimate future value under a constant interest rate and regular compounding.
Cone Surface Area Calculator
Calculate the base and curved surface area of a right circular cone.
Cone Volume Calculator
Calculate the volume of a right circular cone.
Conical Frustum Volume Calculator
Calculate volume of a right circular cone with its tip removed.
Coordinate Distance Calculator
Find Euclidean distance between two points in a plane.
Cylinder Surface Area Calculator
Calculate total surface area of a closed right circular cylinder.
Debt-to-Income Ratio Calculator
Calculate the ratio of entered monthly debt payments to gross monthly income.
Cylinder Volume Calculator
Calculate the volume of a right circular cylinder.
Density Calculator
Calculate average density from mass and volume.
Dilution Calculator
Calculate stock volume needed for a dilution using C₁V₁ = C₂V₂.
Discount Calculator
Work out the sale price and savings from a percentage discount.
Distance Calculator
Estimate distance from average speed and travel time.
Download Time Calculator
Estimate file download time from decimal megabytes and megabits per second.
Ellipse Area Calculator
Calculate ellipse area from its two semi-axis lengths.
Energy Calculator
Estimate electrical energy in kilowatt-hours from watts and hours.
Factorial Calculator
Calculate a factorial for a nonnegative integer up to 170.
Exponent Calculator
Raise a nonnegative base to a real exponent.
Flooring Calculator
Estimate flooring area with an allowance for cutting waste.
Force Calculator
Apply Newton’s second law for constant mass in classical mechanics.
Fraction Addition Calculator
Add two fractions and view a decimal result and unsimplified fraction.
Fraction Multiplication Calculator
Multiply two fractions and see their decimal product.
Free-Fall Time Calculator
Estimate time to fall from rest through a specified distance.
Fuel Consumption Calculator
Calculate fuel consumption in liters per 100 kilometers.
Frequency from Period Calculator
Find frequency from the duration of one complete cycle.
Trip Fuel Cost Calculator
Estimate a trip’s fuel cost using an entered fuel price.
Geometric Sequence Calculator
Find an indexed term in a geometric sequence.
Gravel Calculator
Estimate gravel mass from area, depth, and an entered bulk density.
Greatest Common Divisor Calculator
Find the largest positive integer dividing two nonnegative integers.
Heron’s Formula Calculator
Find triangle area from three side lengths without measuring the height.
Hooke’s Law Calculator
Calculate the restoring-force magnitude of an ideal linear spring.
Hourly to Annual Salary Calculator
Estimate annual gross earnings from hourly pay and paid hours.
Ideal Gas Pressure Calculator
Estimate pressure using the ideal gas law and absolute temperature.
Hydrostatic Pressure Calculator
Calculate pressure increase below the surface of a static fluid.
Uncompressed Image Size Calculator
Estimate uncompressed pixel data size from dimensions and color depth.
Inflation Adjustment Calculator
Estimate the future amount needed under a constant assumed inflation rate.
Kinetic Energy Calculator
Calculate classical translational kinetic energy from mass and speed.
Law of Cosines Calculator
Find a triangle’s third side from two sides and their included angle.
Least Common Multiple Calculator
Find the smallest nonnegative common multiple of two integers.
Length Converter
Convert length measurements with clearly labeled units and instant results.
Remaining Loan Balance Calculator
Estimate remaining principal after a number of equal payments on a fixed-rate loan.
Loan Payment Calculator
Estimate equal monthly payments for a fixed-rate amortizing loan.
Logarithm Calculator
Calculate a logarithm with an entered positive base other than one.
Map Scale Distance Calculator
Convert a distance on a scaled map to real-world distance.
Material Cost Calculator
Estimate material purchase cost from quantity, unit price, and fixed delivery.
Markup Calculator
Calculate a selling price by applying markup to cost.
Molality Calculator
Calculate molality from solute amount and solvent mass.
Moles from Mass Calculator
Calculate amount of substance using entered mass and molar mass.
Molarity Calculator
Calculate molar concentration from solute amount and final solution volume.
Momentum Calculator
Calculate one-dimensional classical momentum.
Mortgage Payment Calculator
Estimate monthly principal and interest for a fixed-rate mortgage.
Mulch Calculator
Estimate mulch volume from bed area and desired depth.
Ohm’s Law Calculator
Calculate current through an ideal resistive element.
Paint Calculator
Estimate liters of paint from area, coats, and product coverage.
Running Pace Calculator
Calculate average running pace from distance and elapsed minutes.
Parallel Resistance Calculator
Find equivalent resistance for two ideal resistors in parallel.
Paver Pack Quantity Calculator
Convert a paving area and allowance into a whole number of product packs.
Parallelogram Area Calculator
Find parallelogram area using a base and its perpendicular height.
Percentage Calculator
Find what percentage a part represents of a whole.
Pendulum Period Calculator
Estimate the period of a simple pendulum for small swings.
Percentage Change Calculator
Compare an original value and a new value to find relative change.
Percentage Decrease Calculator
Apply a percentage decrease to an original value.
Percentage Increase Calculator
Apply a percentage increase and find the new value.
Percentage Error Calculator
Compare a measured value with a nonzero reference using absolute percentage error.
Percentage of a Number
Find a percentage of any nonnegative number.
Pipe Water Volume Calculator
Estimate the internal water capacity of a straight circular pipe.
pH from Hydrogen Ion Concentration Calculator
Estimate pH from hydrogen-ion concentration in a dilute ideal solution.
Permutations Calculator
Count ordered selections without replacement from distinct items.
Pixel Density Calculator
Find display pixel density from resolution and physical diagonal.
Pool Fill Time Calculator
Estimate fill time from required volume and a measured constant flow rate.
Gravitational Potential Energy Calculator
Calculate gravitational potential-energy change in an approximately uniform field.
Power Calculator
Calculate electrical power for DC or ideal resistive loads.
Pressure Calculator
Calculate average pressure from normal force over an area.
Basic Probability Calculator
Find the probability of an event among equally likely outcomes.
Profit Margin Calculator
Calculate gross margin from revenue and the specified cost.
Pythagorean Theorem Calculator
Find the hypotenuse of a right triangle from its two perpendicular sides.
Pyramid Volume Calculator
Find pyramid volume from its base area and perpendicular height.
Race Time Calculator
Estimate finish time at a constant average pace.
Quadratic Equation Calculator
Solve a quadratic equation for its real roots.
Ratio Scaling Calculator
Find an equivalent ratio when the first term is changed.
Recipe Scaling Calculator
Scale an ingredient quantity proportionally to a target serving count.
RC Time Constant Calculator
Find the time constant of a basic resistor-capacitor circuit.
Recurring Savings Calculator
Estimate savings growth with equal end-of-month deposits and monthly compounding.
Rectangle Perimeter Calculator
Find the total boundary length of a rectangle.
Regular Polygon Area Calculator
Find the area of a regular polygon with equal sides and angles.
Reverse Percentage Calculator
Recover an original value after a known percentage increase.
Roof Pitch Calculator
Find roof pitch angle from rise and horizontal run in matching units.
Room Area Calculator
Calculate a rectangular room’s floor area in square meters.
Rule of 72 Calculator
Estimate a doubling time using the Rule of 72 approximation.
Salary to Hourly Calculator
Convert annual gross salary into an equivalent hourly rate.
Sales Tax Calculator
Apply an entered percentage tax rate to a before-tax price.
Savings Goal Calculator
Find the monthly contribution needed to reach a fixed savings goal without assumed returns.
Circle Sector Area Calculator
Find the area of a circular sector from radius and central angle.
Sensible Heat Calculator
Estimate heat transferred during a temperature change without a phase change.
Series Resistance Calculator
Find equivalent resistance for three resistors in series.
Simple Interest Calculator
Estimate interest when interest is calculated only on the original principal.
Slope Calculator
Find the slope of the line through two coordinate points.
Speed Calculator
Find average speed from distance and elapsed time.
Solution Mass Percent Calculator
Calculate a solute’s percentage of total solution mass.
Sphere Surface Area Calculator
Calculate the curved surface area of a sphere from its radius.
Spring Energy Calculator
Calculate elastic potential energy stored in an ideal linear spring.
Spherical Cap Volume Calculator
Find the volume of a spherical cap from sphere radius and cap height.
Sphere Volume Calculator
Calculate the volume enclosed by a sphere from its radius.
Stair Riser Height Calculator
Calculate equal riser height from a total rise and riser count.
Population Standard Deviation Calculator
Calculate population standard deviation for three values.
Square Root Calculator
Find the principal nonnegative square root of a real number.
Steady Heat Loss Calculator
Estimate steady heat transfer through an assembly from U-value, area, and temperature difference.
Successive Discounts Calculator
Apply two consecutive percentage discounts and find the effective discount.
Temperature Converter
Convert temperature measurements with clearly labeled units and instant results.
Tile Calculator
Estimate whole tile quantities from area and tile dimensions.
Tip Calculator
Calculate a percentage tip and divide the resulting bill equally.
Trapezoid Area Calculator
Find a trapezoid’s area from the parallel sides and perpendicular height.
Triangle Calculator
Find triangle area using the base and perpendicular height.
U-Value from Thermal Resistance Calculator
Find thermal transmittance from an entered total assembly resistance.
Unit Converter
Convert common measurements with clearly labeled units and instant results.
Triangular Prism Volume Calculator
Calculate the volume of a prism with a triangular cross-section.
Unit Price Calculator
Compare prices by calculating cost per unit of quantity.
Vector Dot Product Calculator
Calculate the dot product of two two-dimensional vectors.
Remove VAT Calculator
Recover the before-tax price from a tax-inclusive total and an entered VAT rate.
Vector Magnitude Calculator
Find the length of a three-dimensional vector.
Volume Calculator
Find the volume of a rectangular solid from three dimensions.
Volume Converter
Convert volume measurements with clearly labeled units and instant results.
Voltage Divider Calculator
Find the unloaded output of a two-resistor voltage divider.
Wall Area Calculator
Find net rectangular wall area after subtracting doors and windows.
Water Tank Volume Calculator
Estimate water volume in a rectangular tank from internal dimensions.
Wave Speed Calculator
Find wave speed from frequency and wavelength.
Weight Converter
Convert weight measurements with clearly labeled units and instant results.
Weighted Average Calculator
Find the weighted average of two values with nonnegative weights.
Mechanical Work Calculator
Calculate work done by a constant force over a displacement.
Z Score Calculator
Express a value as a number of standard deviations from a supplied mean.
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