Free online calculators that actually explain the math
Free online calculators that actually explain the math. Every tool is quick, works on your phone, and comes with a plain-English explanation, the formula, and a worked example — because a number with no "why" behind it isn't much help.
Finance
Loans, mortgages, savings, taxes, and retirement — work out payments, interest, and take-home pay.
Income Tax Calculator
Estimate your 2026 federal income tax, FICA, effective rate, and take-home pay from your salary and filing status.
FinanceMortgage Refinance Calculator
Compare your current loan to a new one, find your monthly savings, the break-even month, and lifetime interest change.
FinanceSavings Goal Calculator
Find the monthly amount to hit a savings target by a deadline, or see how long your goal will take — interest included.
FinanceCompound Interest Calculator
See how savings grow with contributions, any compounding frequency, and a full year-by-year breakdown.
Math
Percentages, averages, ages, and dates — quick answers with the formula and worked steps.
GPA Calculator
Add a row per course and get your credit-weighted grade point average on the standard 4.0 scale.
MathDate Duration Calculator
Find the time between two dates in years, months, weeks, and days — or add and subtract days from any date.
MathPercentage Calculator
Three tools in one: percent of a number, what percent X is of Y, and percentage increase or decrease.
MathAge Calculator
Find your exact age in years, months, and days, plus total days, weeks, and hours lived.
Health
Body and nutrition tools like BMI and daily calorie needs, in metric or imperial units.
BMI Calculator
Find your body mass index in metric or imperial units and see your weight category.
HealthCalorie Calculator
Estimate your daily calorie needs (TDEE) plus weight-loss and gain targets using Mifflin-St Jeor.
HealthBra Size Calculator
Find your band and cup size from your underbust and bust measurements, plus sister sizes to try.
HealthOne Rep Max Calculator
Estimate your 1RM from a set using six proven formulas, with a percentage-of-1RM training-load chart.
Everyday
Tips, discounts, and unit conversions — the small calculations that come up day to day.
Unit Converter
Convert length, weight, temperature, volume, area, and speed between metric and imperial units instantly.
EverydayTip Calculator
Calculate the tip and total on any bill and split the check evenly between any number of people.
EverydayDiscount Calculator
Find the real sale price and your savings, including stacked second discounts.
Home & Garden
Measure areas and estimate materials for projects around the house and yard.