Keisan Lab
Free calculators for percentages, compound interest, mortgages, dates, ages, tips and more. Every tool runs in your browser and shows the formula with worked examples.
New calculators
- Age CalculatorFree age calculator: enter a date of birth to see your exact age in years, months and days, total days, weeks and months, birth weekday and next birthday.
- Compound Interest CalculatorFree compound interest calculator: enter a starting deposit, monthly contributions, rate and years to see your future balance, interest earned, APY and a yearly table.
- Date CalculatorFree date calculator: count the days between two dates, add or subtract years, months, weeks and days, and see weekdays, weekends and the day of the week.
- Mortgage CalculatorFree mortgage payment calculator: enter price, down payment, rate and term to see your monthly PITI payment with property tax, insurance, HOA dues and PMI.
- Percentage CalculatorFree percentage calculator: find X% of Y, what percent one number is of another, percentage change, percentage difference, discounts and markups, with formulas.
- Tip CalculatorFree tip calculator: enter your bill and sales tax, pick a tip percentage on the pre-tax amount or the full bill, and split the total evenly between up to 100 people.
Finance
- Compound Interest CalculatorFree compound interest calculator: enter a starting deposit, monthly contributions, rate and years to see your future balance, interest earned, APY and a yearly table.
- Mortgage CalculatorFree mortgage payment calculator: enter price, down payment, rate and term to see your monthly PITI payment with property tax, insurance, HOA dues and PMI.
Date & Time
- Age CalculatorFree age calculator: enter a date of birth to see your exact age in years, months and days, total days, weeks and months, birth weekday and next birthday.
- Date CalculatorFree date calculator: count the days between two dates, add or subtract years, months, weeks and days, and see weekdays, weekends and the day of the week.