Age In Weeks Calculator

How to Calculate Your Age in Weeks

Weeks are the unit of pregnancy, infancy, and project planning. The Age in Weeks Calculator shows how many complete seven-day periods have passed since your birth date, with the leftover days reported separately.

How the Calculation Works

The tool first finds the total number of days, then counts how many whole weeks fit inside it:

$$W = \left\lfloor \frac{D}{7} \right\rfloor, \qquad R = D \bmod 7$$

R is the remainder in days, which the tool displays alongside the week total. A common year equals 52 weeks plus one day, and a leap year equals 52 weeks plus two days, which is why week counts drift away from year counts.

Worked Example

Use March 10, 1985 as the birth date and March 10, 2020 as the reference date. That is 35 full years, or 12,784 days. Dividing by seven gives 1,826 complete weeks with 2 days left over:

$$W = \left\lfloor \frac{12{,}784}{7} \right\rfloor = 1{,}826 \text{ weeks}, \qquad R = 2 \text{ days}$$

For bigger and smaller views of the same span, see the Age in Months Calculator or the Age in Days Calculator.