Free online calculators that show their working
Grades, loans, dates, math and more. Every calculator explains the formula it uses, works on any device and keeps your numbers in your browser.
- 141 calculators and growing
- Formulas shown
- No sign-up
- Private: nothing is uploaded
Browse by category
- Math & ScienceAlgebra, geometry, statistics, calculus and chemistry calculators with the working shown.
- Money & FinanceLoans, interest, pay, taxes and investing calculators that show every number they use.
- School & GradesGrade, GPA, final exam and test score calculators for students and teachers.
- Dates & TimeCount days between dates, add time, work out ages and convert hours.
- Home & BuildingConcrete, gravel, tile, flooring and other material calculators for home projects.
- Health & FitnessStrength, calorie, body and fitness calculators based on published formulas.
- Sports, Auto & MoreGear ratios, horsepower, sports stats, music and everyday calculators.
Math & Science
All math →- Factor CalculatorList all factors, factor pairs and the prime factorization.
- Area CalculatorArea of rectangles, circles, triangles and 5 more shapes.
- Average CalculatorMean, median, mode and range of any list of numbers.
- Perimeter CalculatorPerimeter and circumference of common shapes.
- Percentage CalculatorPercent of a number, percent change and more.
- Fraction CalculatorAdd, subtract, multiply and divide fractions with steps.
Money & Finance
All finance →- Salary to Hourly CalculatorConvert yearly salary to hourly pay, or hourly to salary.
- HELOC CalculatorEstimate your HELOC limit and draw and repayment payments.
- Compound Interest CalculatorGrow savings with compounding and regular deposits.
- Debt-to-Income Ratio CalculatorDebt-to-income ratio and what mortgage lenders allow.
- Loan Repayment CalculatorMonthly payment, total interest and payoff schedule.
- Mortgage CalculatorMonthly house payment with tax, insurance and PMI.
School & Grades
All school →- Grade CalculatorWork out your overall grade from weighted scores or points.
- Weighted Grade CalculatorCombine category grades using their percentage weights.
- Final Grade CalculatorSee the score you need on your final exam to reach your goal.
- GPA CalculatorSemester and cumulative GPA from grades and credits.
- High School GPA CalculatorWeighted and unweighted GPA with honors and AP classes.
Dates & Time
All dates →- Chronological Age CalculatorExact age in years, months and days for test scoring.
- Day CalculatorAdd or subtract days, weeks or months from a date.
- Date Duration CalculatorCount days, weeks and months between two dates.
- Time Duration CalculatorHours and minutes between two times, overnight included.
- Business Day CalculatorCount or add working days, skipping weekends and holidays.
- Age CalculatorExact age in years, months and days on any date.
Home & Building
All home →- Concrete CalculatorCubic yards and bags of concrete for slabs and columns.
- Cubic Yard CalculatorCubic yards of mulch, soil, gravel or fill for any area.
- Gravel CalculatorTons and cubic yards of gravel, rock or sand for a project.
- Tile CalculatorHow many tiles and boxes you need for a floor or wall.
- Cubic Feet CalculatorVolume in cubic feet, yards, meters and gallons.
- Flooring CalculatorSquare feet, boxes and cost of flooring.
Health & Fitness
All health →- One Rep Max CalculatorEstimate your 1RM and training weights from any set.
- Steps to Miles CalculatorConvert steps to miles and km, or miles to steps.
- BMI CalculatorBody mass index, category and healthy weight range.
- TDEE CalculatorDaily calorie burn from BMR and activity level.
- Race Pace CalculatorPace per mile and km, speed and splits for any race.
- Ideal Weight CalculatorIdeal body weight formulas and healthy BMI range.
Sports, Auto & More
All more →- Gear Ratio CalculatorGear ratio, output RPM and torque from tooth counts.
- Horsepower CalculatorHorsepower from torque and RPM, plus kW.
- Engine Displacement CalculatorEngine size from bore, stroke and cylinders.
- PPI CalculatorPixel density of any screen.
- ERA CalculatorEarned run average from runs and innings.
- Words to Minutes CalculatorHow long your speech or text takes to say or read.