25 Free Calculators
for real life

Why a Life Calculator Library?

Most of life's important decisions are tied to time. How much should you save each month if you want to retire at 60? How many weeks pregnant are you today? How many working days are left before a deadline? How much will $1,000 be worth after ten years of inflation? Each of these questions has a precise answer, but the math behind it is easy to get wrong on a napkin. We built this library so you can get a reliable answer in seconds, understand how it was calculated, and then make your own decision with better information.

How we build every calculator

• Published formulas only. Finance tools use the standard time-value-of-money equations used by banks and textbooks. Health tools use clinically published equations such as Mifflin-St Jeor, Naegele's rule and the WHO BMI categories. Date tools follow the Gregorian calendar rules, including leap years.
• The method is shown on the page. Each tool explains the formula it uses, gives a worked example and lists its limitations, so you are never looking at a black box.
• Privacy by design. Every number you type stays on your device. Nothing is sent to a server, nothing is stored, and no account is required.
• Reviewed and updated. We re-check the formulas, examples and reference values regularly. This library was last reviewed in October 2026.

Educational, not advice

Calculators are excellent for exploring scenarios, but they cannot know everything about your situation. Treat the money tools as a planning aid rather than financial advice, and treat the health tools as general information rather than a medical opinion. When the stakes are high, use the result as a starting point for a conversation with a qualified professional.

Have an idea for a calculator we should add, or spotted a mistake? Contact us — every message is read by a person.