Fitness & Health

Pregnancy Conception Calculator

Estimate conception date and likely fertile window from an expected due date.

Inputs

Results update as you edit.

Estimated due date

Estimated conception date

Feb 13, 2026

Results update as the calculator inputs change.

This is an estimate only and is not medical advice.

Likely fertile window start

Feb 8, 2026

Likely fertile window end

Feb 14, 2026

Estimated LMP

Jan 30, 2026

Due date

Nov 6, 2026

How to Estimate Conception Date

Known Due Date

The due date is used as the anchor for estimating conception timing.

266-Day Estimate

Conception is often estimated at about 266 days before the due date.

Fertile Window

The likely fertile window spans several days because ovulation and sperm survival vary.

How to Interpret a Conception Estimate

Conception estimates are approximate. The date can vary based on ovulation timing, cycle length, ultrasound dating, and the due-date method used by a clinician.

What Affects Conception Estimates?

Due Date Accuracy

The conception estimate is only as accurate as the due date.

Ovulation Timing

Ovulation can happen earlier or later than the textbook midpoint.

Cycle Variation

Irregular cycles widen the possible conception window.

Ultrasound Dating

Early ultrasound can shift the estimated pregnancy timeline.

Biology

Fertilization and implantation timing vary naturally.

Clinical Context

Use provider dating for medical or legal questions.

Conception Date Uses

Date Estimate

Count backward from due date to estimate conception timing.

Window Planning

Review a range rather than relying on one exact day.

Pregnancy Timeline

Connect conception estimate with gestational age milestones.

Frequently Asked Questions

Can this tell the exact conception date?

No. It estimates a likely date and window, but conception timing cannot usually be known exactly from a calculator.

Why count back from the due date?

A typical model estimates conception at about 38 weeks before the due date.

Can ultrasound change the estimate?

Yes. Early ultrasound can revise the clinical estimate of gestational age and due date.

Does this identify paternity?

No. It cannot determine paternity or replace medical or legal testing.

Should I use this for medical decisions?

No. Use dates confirmed by your obstetric care team.