Age Calculator

Calculate your exact age in years, months, weeks and days, compare two ages, find a birth-date range from a completed age, or list birthday milestones and countdowns. Everything runs in your browser — dates and names never leave your device.

How to use it: choose Calculate age and enter the date of birth with the day, month and year fields. Keep the reference date as today, or set any past or future date such as an application cutoff, then press Calculate to see completed years, months, weeks, days and the birthday countdown. The Compare ages tab measures the gap directly between two birth dates; Find birth-date range returns a range from a completed age; Milestones lists upcoming year and day milestones with calendar downloads.

Completed years versus totals: completed years count anniversaries (you turn 30 on your 30th birthday, not 30 x 365 days later) while total calendar days count midnights between the two dates — leap years and uneven months mean days divided by 365 never gives completed years, so this calculator never divides that way. For babies the result also highlights months and weeks (for example 14 months old) because 0 years is unhelpful at that age; the calculation is identical, only the presentation changes.

Month-end, leap-day and time conventions: month arithmetic clamps to the last day of the destination month (31 January plus one month is 28 February, 29 in a leap year; plus two months is 31 March, with no drift). For 29 February births you choose whether non-leap anniversaries fall on 28 February (default) or 1 March, applied to ages, countdowns and year milestones alike. All dates use the proleptic Gregorian calendar (divisible by 4, except centuries unless divisible by 400). Calendar days count date boundaries while elapsed hours count actual durations between two instants in stated time zones: nonexistent spring-forward times are rejected and repeated autumn times ask you to pick the earlier or later occurrence.

Reverse ranges, cutoffs and privacy: hundreds of birth dates share the same completed age, so Find birth-date range returns the full inclusive range — never a single exact date — with both boundaries verified by the forward calculation. For eligibility questions, set Calculate age on to the stated cutoff date and read the completed years; whether that meets any rule always depends on the organisation, never on age alone. Every calculation runs locally with no server, analytics, storage or share links; copied summaries include the reference date and convention while birth dates and names are excluded unless you tick the box, and Reset clears inputs and restores today.