Calculators10 tools

Free online calculators with exact answers for dates and ages

Calendar arithmetic looks trivial until you try it by hand. Months run 28 to 31 days, leap years add a day most years but not all, and 'how many days between these two dates?' is exactly the kind of question humans get wrong by one. The calculators in this category apply real calendar rules so the answer is exact, and they do it instantly, in your browser, without storing anything you enter.

The age calculator converts a date of birth into an exact age in years, months and days, plus total days lived and a countdown to the next birthday. That precision matters more often than you would expect. School admission cutoffs, sports age categories, visa and insurance forms, and HR paperwork all ask for exact ages, where 'about 34' is not an acceptable answer. It is equally happy calculating a child's age in months, an ancestor's age at emigration, or the day you turn 10,000 days old.

The date difference calculator measures the exact gap between any two dates, shown as days, weeks, months and years at the same time. Point it backward to measure durations: length of service, invoice ageing, how long a project actually took. Point it forward for countdowns: days until the wedding, the exam, the launch, the visa deadline. Leap years and month lengths are handled exactly, which is precisely where spreadsheet formulas and mental math slip.

The everyday money ones get used the most. The tip calculator splits a bill and can round each share up to a whole dollar, the discount calculator shows why 20% off followed by an extra 10% is a 28% cut and not 30%, and the sales tax calculator adds tax to a price or pulls it back out of a receipt total with an editable rate, because combined US rates vary by city.

For the rest of daily arithmetic there is the percentage calculator and the percentage increase calculator for the three questions people actually ask about percentages, the unit converter for length, weight, volume and temperature, the fuel cost calculator for a trip in US, UK or metric units, and the GPA calculator with a credit-weighted 4.0 scale you can edit when your school publishes different points.

The two calculators complement each other nicely. Birth date questions go to the age calculator, and everything else on the calendar goes to the date difference tool. Once your date math is done, the rest of the site helps with what comes next: a scannable invitation link from the QR code generator for the event you counted down to, or a fair draw from the random number generator at the party itself. Free, instant and exact, with no signup required.