Ovulation Calculator Gender Predictor

Track cycle patterns and likely ovulation dates accurately. Compare timing entries, predictions, and exportable summaries. Use results carefully because no method can guarantee sex.

Calculator

Last period start date

Average cycle length

Luteal phase length

Typical period length

Known conception date

Recent cycle lengths

Intercourse dates

Enter dates separated by commas. The predictor uses timing theory only.

Example Data Table

Last Period Start	Cycle Length	Luteal Phase	Intercourse Dates	Predicted Ovulation	Theory Result
2026-04-01	28 days	14 days	2026-04-11, 2026-04-13	2026-04-15	Girl-leaning timing theory
2026-05-02	30 days	14 days	2026-05-17, 2026-05-18	2026-05-18	Boy-leaning timing theory
2026-06-10	27 days	13 days	2026-06-18	2026-06-24	Outside common fertile timing range

Formula Used

Predicted ovulation date = last period start date + cycle length - luteal phase length.

Fertile window = predicted ovulation date - 5 days through predicted ovulation date + 1 day.

Estimated due date from last period = last period start date + 280 days.

Estimated due date from conception = conception date + 266 days.

Average cycle length = sum of recent cycle lengths ÷ number of cycles entered.

Timing-based predictor compares intercourse timing against predicted ovulation. Earlier fertile-window timing is often labeled girl-leaning, while timing closest to ovulation is often labeled boy-leaning. This is only a traditional theory and not a medical predictor.

How to Use This Calculator

Enter the first day of your last menstrual period.
Enter your average cycle length and luteal phase length.
Optionally add recent cycle lengths to improve the average.
Optionally add intercourse dates for timing analysis.
Optionally enter a known conception date for due-date estimation.
Click calculate to show the result above the form.
Review the fertile window, ovulation estimate, and timing note.
Use CSV or PDF export if you want a saved copy.

Important Note

This tool is for cycle planning and education. It does not confirm ovulation, pregnancy, fertility, or fetal sex. For fertility concerns, irregular cycles, pain, bleeding, or pregnancy questions, speak with a qualified clinician.

FAQs

1. Can this calculator guarantee baby sex?

No. It cannot guarantee or confirm baby sex. The timing method shown here is only a traditional theory and should be treated as informational.

2. How does the ovulation estimate work?

It subtracts the luteal phase from the cycle length, then counts forward from the first day of the last period.

3. What if my cycles are irregular?

Use recent cycle lengths in the form. The calculator averages them, but irregular cycles still reduce timing accuracy.

4. Why does the fertile window start five days earlier?

Sperm may survive for several days. That is why fertility planning usually starts before the predicted ovulation date.

5. What is the luteal phase?

It is the time between ovulation and the next period. Many people use about 14 days, though it varies.

6. Which due date is better?

The last-period estimate is common for general planning. A confirmed conception date can refine the estimate when known.

7. Why is the prediction confidence very low?

Because timing around ovulation does not reliably determine baby sex. Medical confirmation requires proper clinical methods later in pregnancy.

8. Can I export the result?

Yes. The page includes CSV and PDF download buttons after a calculation is completed.