Conception Date Estimator

Estimate when you conceived and your due date. Free, private and instant.

How to use the Conception Date

  1. Choose I know my: Last period date or Due date.
  2. Answer any extra questions that appear for your choices.
  3. Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.

About the Conception Date

Work out when conception most likely happened and your estimated due date using your last period or your due date. Conception usually occurs about two weeks after the first day of the last period, around ovulation.

Also known as: conception calculator, when did I conceive, date of conception calculator, conception date from due date.

Worked example

Dates in this example are worked out as if today were 5 Nov 2026.

Estimated conception date: 5 Nov 2026 (2 weeks 0 days pregnant today). Conception most likely happened around 5 Nov 2026, within a window of 2 Nov - 6 Nov 2026. The estimated due date is 29 Jul 2027.

Formula and cut-offs

Conception = last period + cycle length - 14 days. Due date = last period + 280 days (adjusted for cycle length). Gestational age counts from the last period, so it is about 2 weeks more than the baby’s age.

Frequently asked questions

How is the conception date estimated?

About 14 days after the first day of your last period, or 266 days before your due date.

Why is gestational age 2 weeks ahead?

Pregnancy is dated from your last period, which is about 2 weeks before conception.

How accurate is a due date?

Only about 5% of babies arrive on the due date. An early ultrasound gives the most accurate dating.

When did I conceive if my last period started on 22 Oct 2026 and my cycle is 28 days?

Conception most likely happened around 5 Nov 2026, within a window of 2 Nov - 6 Nov 2026. The estimated due date is 29 Jul 2027. This example treats 5 Nov 2026 as today. Enter your own dates above for a personal result.

Sources and references

Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.

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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.