How is ovulation estimated?

For a regular cycle, ovulation is estimated as cycle length minus 14 days from the first day of your last period. Your fertile window includes the five days before and the day of ovulation.

Is this a form of contraception?

No. This calculator estimates when you may be most fertile — it is not reliable for preventing pregnancy. If you're trying to avoid pregnancy, use a proven method and speak with a clinician.

What if my cycle is irregular?

Irregular cycles make ovulation harder to predict. Ovulation predictor kits, basal body temperature tracking or a fertility specialist can give a more personal picture.

Ovulation Calculator

Estimate your fertile window and ovulation day. Private and instant — no account required.

First day of your last period

Average cycle length28 days

Estimated ovulation

Monday, October 19, 2026

Fertile window: Oct 14 – Oct 19, 2026

Next period expected: Nov 2, 2026

This calculator estimates your most fertile days — it is not a form of contraception. If you're trying to avoid pregnancy, please use a proven method.

October 2026

Highlighted: fertile window. Filled: estimated ovulation day.

Related calculators

Due date calculator
Reverse due date calculator
Conception due date calculator
How many weeks pregnant am I?

How this page is sourced

SoftBump calculators use the standard dating rules published by national health bodies. Every result is an estimate, and your midwife, obstetrician or fertility team always takes priority over anything shown here.

NHS — You and your baby at 0 to 8 weeks pregnant
ACOG — Methods for estimating the due date

Last reviewed: March 2026

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