How does the ovulation calculator work?

It counts 14 days back from your next expected period to estimate ovulation. The next period is your last period start plus your cycle length.

What is the fertile window?

In this calculator it is the 5 days before ovulation, the day of ovulation and the day after. It is an estimate based on the calendar.

Less so. When cycle length changes from month to month, ovulation can shift too. Neva shows a range of days instead of a single date in that case.

No. It gives estimates only and is not a method of contraception.

No. Everything is calculated in your browser and nothing is stored or sent anywhere.

Enter the first day of your last period and your cycle length to estimate your ovulation date and fertile window.

First day of your last period

Cycle length (days)

Ovulation is estimated 14 days before your next period. The fertile window runs from 5 days before ovulation to 1 day after, the same as in Neva.

Your dates never leave this page. Everything is calculated in your browser, and nothing is saved or tracked.

Estimates only. Not a method of contraception. Not medical advice.

How does the ovulation calculator work?: It counts 14 days back from your next expected period to estimate ovulation. The next period is your last period start plus your cycle length.
What is the fertile window?: In this calculator it is the 5 days before ovulation, the day of ovulation and the day after. It is an estimate based on the calendar.
Is it accurate if my cycle is irregular?: Less so. When cycle length changes from month to month, ovulation can shift too. Neva shows a range of days instead of a single date in that case.
Can I use it as birth control?: No. It gives estimates only and is not a method of contraception.
Do you save the dates I enter?: No. Everything is calculated in your browser and nothing is stored or sent anywhere.