Safe period calculator

Estimate ovulation, the fertile window and relatively safer days from your cycle. For reference only — do not rely on this alone for contraception.

First day of last period

Use the first day bleeding started

Cycle length28 days

Days from day 1 of one period to day 1 of the next (often 28)

Period length5 days

How many days bleeding usually lasts

Choose the first day of your last period