LMP Apr 1, 2026, 28 day cycle
- Fertile window
- Apr 10, 2026-Apr 15, 2026
- Next period
- Apr 29, 2026
- Luteal phase
- 14 days
Conception Calculator
Use this free conception calculator to estimate conception date and fertile window from last period, cycle length, and luteal phase.
Research-based formula Estimate limits shown Examples included Private history
Formula steps
- Estimate the next period from the last period date and cycle length.
- Subtract the luteal phase length to estimate ovulation.
- Show the fertile window as the five days before ovulation through ovulation day.
How to use the conception calculator
- Enter the requested measurements, dates, lab values, or workout details.
- Check that the units and formula assumptions match what the tool is asking for.
- Press the calculate button to see the answer, supporting metrics, and formula steps.
- Read the estimate with the health disclaimer in mind, then copy the result if you need it for notes.
Common uses
Estimate conception timing from cycle data.
Find a fertile window for regular cycles.
Compare conception estimates with due-date estimates.
Understand that ovulation can vary month to month.
Examples
Approximate conception date
Later estimated ovulation
Cycle-based estimate
Frequently asked questions
Quick answers about formulas, inputs, estimate limits, professional guidance, examples, and private in-browser history.
What can I use the Conception Calculator for?
Use it for quick educational estimates, planning, comparison, and trend checks. Health and fitness results should be interpreted with context, not as a diagnosis.
How does the Conception Calculator calculate the result?
The calculator estimates ovulation as next period date minus luteal phase length, then uses that as an approximate conception date.
Is this medical advice?
No. This page provides an educational estimate only. Talk with a qualified health professional before making medical, pregnancy, nutrition, medication, or safety decisions.
Are my health inputs private?
Yes. The calculator runs in your browser tab. Recent answers stay only on the page while you use it and are not sent to a server.