For the best result, enter the first days of your last three menstrual periods in order. If you only remember the first day of the most recent period, enter that date below:

First day of your most recent period:

If you enter only the most recent period date, the calculator assumes a 28-day cycle. The preceding period would then probably have started on the date below:

First day of the period before your most recent one:

For a more accurate result, change the date below if you now remember it:

First day of the period two cycles before your most recent one:

Based on your entries, your cycles last approximately days, and your next period will probably start on .

The days when your chances of conceiving are highest:

to your ovulation day, .

Please note: do not use this calculator for contraception. Cycles shorter than 21 days or longer than 35 days may indicate that ovulation is not occurring. If this applies to you, consult your doctor for gynaecological assessment.