Free Online Calculators – Percentages, Dates, Loans and Interest
Percentage, discount, age, date difference, loan, compound interest, mortgage, hours, GPA and sales tax calculators with clear results and calculation details. Free and private.
- Percentage Calculator
Work out X% of a number, what percent one number is of another, the percentage change between two values, and the difference in percentage points. Shows the formula.
- Discount Calculator
Find the sale price after a discount, the discount percentage between two prices, and the real total when discounts are stacked. Formula shown for every result.
- Age Calculator
Enter a date of birth to get an exact age in years, months and days, the number of days until the next birthday, and how many days and weeks old someone is.
- Date Calculator
Count the days, weeks and months between two dates, add or subtract days from a date, count weekdays, and see a D-day countdown. Free and time-zone safe.
- Loan Calculator
Enter a loan amount, interest rate and term to see the monthly payment, total interest and a full amortization schedule. Compare repayment methods and download a CSV.
- Compound Interest Calculator
See how savings grow with compound interest. Enter a starting amount, monthly contributions, rate, time and compounding frequency, and compare the result with simple interest.
- Mortgage Calculator
Estimate your monthly mortgage payment including principal, interest, property tax, home insurance, PMI and HOA fees. See the full amortization schedule and when PMI ends.
- Hours Calculator
Add up hours worked for each day of the week, subtract unpaid breaks, handle overnight shifts, and see total hours in both hours:minutes and decimal. Add your hourly rate to estimate gross pay with overtime.
- GPA Calculator
Calculate your GPA on the 4.0 scale from letter grades and credit hours. See weighted GPA for Honors and AP classes, and combine this semester with your current cumulative GPA.
- Sales Tax Calculator
Add sales tax to a price, back out the tax from a total, or find the tax rate from a receipt. Fill in any state's average combined rate for 2026 and see the tax rounded to the cent.
Calculators that show their work
A result is more useful when you can see how it was calculated. Many calculators here show a formula, a breakdown or a payment schedule alongside the answer, so you can check the logic or explain it to someone else. Inputs update the result immediately, and nothing you type is sent to a server.
What you can calculate
- Percentages and discounts. Find a percentage of a number, the percentage change between two values, the difference in percentage points, a sale price after one or more discounts, or the discount rate from an original and sale price.
- Ages and dates. Work out an exact age in years, months and days, count the days between two dates, or find the date a given number of days from today.
- Loans and mortgages. Compare monthly payments and total interest for different repayment methods, then review the full payment schedule month by month and download it as a CSV file for your own spreadsheet.
- Savings and investments. See how compound interest grows a lump sum or regular deposits over time, and how much of the final balance comes from interest.
- Work and school. Total the hours on a weekly time card with breaks, overnight shifts and overtime, or work out a semester and cumulative GPA, weighted or unweighted.
- Shopping and sales tax. Add sales tax to a price, back it out of a receipt total, or find the rate that was charged, with 2026 average rates for every state.
How to read the results
Financial calculators use the numbers you enter and standard formulas. Real products add details that a general calculator cannot know, such as fees, insurance, rate changes, rounding rules or taxes that differ by country. Treat the results as an estimate for comparing options, not as a quote. When the stakes are high, confirm the figures with your lender or a qualified adviser.
Rounding is another common source of small differences. The loan and mortgage schedules round payments and interest to cents and adjust the final payment for any remaining balance. A lender may use a different rounding convention, so its total may differ slightly from the estimate here.
If a result looks surprising, check the units first: an annual rate entered where a monthly rate was expected, or a term in years entered as months, explains most mistakes.