Ovulation Calculator

Enter the first day of your last period and your average cycle length to estimate ovulation, fertile window, peak days, and the next period.

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Estimated result for this cycle

Aug 29, 2026

Estimated ovulation

Estimate confidence

86%

Estimated ovulation

Aug 29, 2026

Higher fertility window

Aug 24, 2026 - Aug 30, 2026

Estimated next period

Sep 12, 2026

LH test start guide

Aug 25, 2026

Cycle timeline

Cycle day today 19

Aug 15, 2026-Sep 11, 2026Peak reference days: Aug 28, 2026 - Aug 29, 2026

The estimated ovulation date for this cycle has passed.

Cycle details

Use averages if exact dates vary. This tool is best for planning and cycle awareness, not diagnosis.

First day of last periodReference dateAverage cycle lengthLuteal phase lengthAverage period lengthCycle regularity

Next 3 cycles preview

Days to ovulation: 4 days

#1 Cycle start

Aug 15, 2026

Fertile window: Aug 24, 2026 - Aug 30, 2026
Ovulation: Aug 29, 2026
Next period: Sep 12, 2026

#2 Cycle start

Sep 12, 2026

Fertile window: Sep 21, 2026 - Sep 27, 2026
Ovulation: Sep 26, 2026
Next period: Oct 10, 2026

#3 Cycle start

Oct 10, 2026

Fertile window: Oct 19, 2026 - Oct 25, 2026
Ovulation: Oct 24, 2026
Next period: Nov 7, 2026

Health use notice

This tool is for general reference only and does not replace medical, nutrition, diagnostic, or treatment advice. For health decisions, confirm the result with a clinician, registered specialist, or official guidance.

Practical tips

check_circleOvulation is often estimated from the next expected period, but individual timing can vary.
check_circleFor conception planning, look at the wider window from several days before ovulation through the day after.
check_circleIf cycles are irregular, combine this estimate with LH tests, basal temperature, and cervical mucus tracking.

Health reference notice

This calculator is an educational estimate and does not replace contraception, diagnosis, or medical care. For irregular cycles, severe pain, unusual bleeding, possible pregnancy, or fertility concerns, consult a clinician.

How the ovulation estimate works

The calculator estimates the next period from your average cycle length, then counts backward by the luteal phase length. It shows a wider fertile window to make planning easier.

Usage notes

Next period = last period start + average cycle length
Estimated ovulation = next period - luteal phase length
Fertile window = 5 days before ovulation through the day after ovulation
LH test start guide = 4 days before estimated ovulation

Frequently asked questions

Can I use this calculator for contraception?expand_more

No. This is not a contraceptive method. Ovulation can shift with stress, sleep, illness, medication, and cycle changes.

What if my cycle is irregular?expand_more

Use the average of the last 3-6 cycles and treat the result as a broad range. If variation is large or periods are often missed, consider medical advice.

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