18 calculators and counting
Free online calculators that just work
Finance, health, and everyday math — accurate tools with the formulas explained, no sign-up and nothing to install.
Most used
The tools people reach for most often.
Loan & EMI Calculator
Monthly payment, total interest, and a full amortization schedule.
OpenMortgage Calculator
Full monthly cost including tax, insurance, and PMI.
OpenBMI Calculator
Body mass index with category and healthy weight range.
OpenCalorie & BMR Calculator
Daily calorie needs for losing, holding, or gaining weight.
OpenPercentage Calculator
Every common percentage question in one place.
OpenAge Calculator
Exact age in years, months, days, and total units.
OpenFinance
Work out loan payments, investment growth, and what things actually cost.
Loan & EMI Calculator
Monthly payment, total interest, and a full amortization schedule.
OpenMortgage Calculator
Full monthly cost including tax, insurance, and PMI.
OpenCompound Interest Calculator
See how savings grow with regular contributions.
OpenSIP Calculator
Project returns on a monthly investment plan.
OpenDiscount Calculator
Final price after one or two discounts, plus tax.
OpenTip Calculator
Tip amount and per-person split, rounded cleanly.
OpenHealth & Fitness
Track body composition, calorie needs, and the numbers behind your goals.
BMI Calculator
Body mass index with category and healthy weight range.
OpenCalorie & BMR Calculator
Daily calorie needs for losing, holding, or gaining weight.
OpenBody Fat Calculator
Body fat percentage from tape measurements.
OpenIdeal Weight Calculator
Target weight from four clinical formulas plus BMI range.
OpenPregnancy Due Date Calculator
Due date, current week, and trimester milestones.
OpenWater Intake Calculator
Daily hydration target adjusted for exercise and climate.
OpenMath & Everyday
Percentages, dates, grades, and the quick arithmetic that comes up daily.
Percentage Calculator
Every common percentage question in one place.
OpenAge Calculator
Exact age in years, months, days, and total units.
OpenDate Difference Calculator
Days between two dates, with or without weekends.
OpenGPA Calculator
Weighted GPA from course grades and credit hours.
OpenFraction Calculator
Add, subtract, multiply, and divide fractions.
OpenAverage Calculator
Mean, median, mode, range, and standard deviation.
OpenWhy The Calc Library?
No sign-up, ever
Every calculator is free and open. No account, no paywall, no email capture before you get an answer.
Runs in your browser
Calculations happen on your device. Your numbers are never sent to a server or stored anywhere.
Shows the working
Each tool explains the formula it uses and what the result means, so you can check it yourself.