Calculators
Straightforward calculators for percentages, dates, interest, and everyday numeric work.
Available now
About Calculators
Three calculators for everyday numbers: percentages, exact age and compound interest. They run in your browser, so the values you enter are not uploaded, and none of them need an account.
All 3 tools here run entirely in your browser.
Percentages
Find X% of a number, work out what percentage one number is of another, or calculate the percentage change between two values. Decimal values such as 2.5% work in all three modes. It is handy for discounts, tips, grades and price changes.
Exact age
Enter a date of birth to see an exact age in years, months and days, the total number of days lived and how many days remain until the next birthday. Age is calculated as of today.
Compound interest
Enter a starting amount, an annual rate, a number of years and how often interest compounds: annually, semi-annually, quarterly, monthly or daily. You get the final amount, the interest earned and a year-by-year table. It models a single lump sum, so regular contributions are not included.
How the results are worked out
Percentage change is ((new − original) / |original|) × 100, so a positive result is an increase and a negative one is a decrease. Compound interest uses A = P × (1 + r/n)^(n×t), where P is the principal, r the annual rate as a decimal, n the number of compounds per year and t the number of years. The age calculator counts whole months from the birth date and clamps to the end of shorter months, and a 29 February birthday is observed on 28 February in non-leap years.
Frequently asked questions
Are my numbers sent to a server?
No. All three calculators run in your browser, so what you type is not uploaded.
Do I need an account to use the calculators?
No. The calculators are free to use without signing in.
Can the compound interest calculator include monthly deposits?
Not at the moment. It calculates growth on a single lump-sum principal, with no recurring contributions.
Can I calculate someone's age on a past or future date?
The age calculator works out age as of today. There is no reference-date option yet.