Ovulation Calculator

When to use?

Use it to estimate your ovulation day and fertile window by entering your last period start date and average cycle when planning a pregnancy or tracking fertility.

How to use

• Enter the last period start date.
• Enter the average cycle length (days; default 28).
• The estimated ovulation day and fertile window are shown.

Input Explanation

Enter the last period start date and your usual cycle length.

Calculation Basis

Ovulation = next expected period − 14 days. Fertile window = 5 days before ovulation through the day after. Irregular cycles increase the error.

Usage Examples

• Estimate the fertile window - See the estimated ovulation day and fertile range from your average cycle.
• Plan a pregnancy - Identify the days with the highest chance of conception to plan.
• Track your cycle - Gauge the next expected period and ovulation to manage your schedule.

Examples

• Period Jan 1, cycle 28 → ovulation Jan 15, fertile Jan 10–16
• Period Mar 1, cycle 30 → ovulation Mar 17, fertile Mar 12–18

Cautions

• An irregular cycle lowers prediction accuracy. Consult a professional for contraception or pregnancy planning.
• Time-zone settings can cause a one-day difference in some cases.

Guides

How ovulation is estimated

It estimates ovulation about 14 days before the next expected period and shows the surrounding days as the fertile window.

Individual and cycle variation

Irregular cycles or changing health can increase the error. Contraception or pregnancy decisions need professional advice.

FAQ

Is the ovulation day exact?

It varies by individual, so it is a reference. Irregular cycles increase the error.

How is ovulation estimated?

It treats about 14 days before the next expected period as ovulation, with surrounding days as the fertile window.

How long is the fertile window?

This tool shows about 7 days, from 5 days before ovulation through the day after.

Can I use it for contraception?

It is an estimate and not reliable for contraception. Use proper contraceptive methods.

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