How do I calculate my pregnancy due date by conception date?

Choose the Conception method and enter the date you believe conception happened. The tool adds 266 days to that date — the standard obstetric offset. Conception usually happens around ovulation, about 14 days after your last period in a 28-day cycle, so the LMP method (280 days) and conception method usually agree within a day or two.

How do I calculate a due date for an IVF pregnancy?

Choose the IVF method, enter your embryo transfer date, and select the embryo age: Day 3 or Day 5. The tool adds 263 days for a Day 3 transfer or 261 days for a Day 5 transfer, matching standard clinical IVF dating. For a Day 5 example: a February 1, 2026 transfer gives an October 20, 2026 due date.

How accurate is a pregnancy due date calculator?

Treat it as an estimate, not a prediction: only about 1 in 20 babies is born on the estimated due date, and a ±2 week window is completely normal. Naegele's rule assumes regular 28-day cycles; irregular cycles, late ovulation, and individual factors all shift the real date. Use the result to plan appointments, then confirm dates with your clinician — especially from an early ultrasound, which dates more precisely.

What is a Naegele's rule due date calculator?

It is the classic obstetric formula this tool uses for the LMP method: add 280 days (40 weeks) to the first day of your last menstrual period. Naegele's rule is the default dating method clinicians use before an ultrasound confirms things — the tool applies it exactly, plus 266 days for conception dates and clinical offsets for IVF transfers.

Pregnancy Due Date Calculator

Q: How many weeks pregnant am I — calculator?

This calculator gives you a "how many weeks pregnant am I" answer instantly: it counts whole days from your LMP (or LMP-equivalent) to today and shows weeks plus extra days, e.g. "24w 3d". Pick the LMP method, enter the first day of your last period, and run the tool — the gestational age line shows your current week.

Q: What trimester am I in — calculator?

The trimester line uses the standard bands: 1st trimester is weeks 1–13, 2nd is weeks 14–26, and 3rd is weeks 27–40. Enter your LMP (or conception/IVF date) above and the tool shows your current trimester alongside your gestational age — e.g. "2nd Trimester" at week 20.

What is Pregnancy due date calculator?

Pregnancy Due Date Calculator — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.

The engine is the open-source pregnancy-due-date-calculator (DarnOsint, MIT), using standard obstetric rules: Naegele's rule adds 280 days to the first day of your last menstrual period (LMP); conception-date mode adds 266 days; IVF mode adds 261 days after a Day 5 transfer or 263 days after a Day 3 transfer. Gestational age is the whole days between the LMP-equivalent date and today, expressed as weeks plus days; trimesters follow the 1–13 / 14–26 / 27–40 week bands; the 12 dated milestones come from the engine's week table (heartbeat around week 6, anatomy scan around weeks 18–20, viability at week 24, full term at week 37). If you enter a cycle length, the estimated conception date shifts to LMP + (cycle length − 14) instead of the default 28-day assumption. Limitations: only about 1 in 20 babies arrives on the estimated due date — treat it as a ±2-week guide, not a prediction; the estimate assumes regular cycles and cannot account for individual medical factors. This is an informational estimate, not medical advice — confirm dates with your clinician.

Why use this pregnancy due date calculator?

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Built for pregnancy due date calculator

Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.

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Transparent & honest

Informational only — not medical advice; confirm your dates with a doctor or midwife.

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Private by design

Everything runs in your browser. Your inputs never leave your device.

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Works everywhere

Fully responsive — perfect on desktop, tablet, and mobile. No app needed.

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Regularly updated

Regularly maintained and reviewed to ensure accuracy.

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Free forever

No accounts, no limits, no watermarks. Use Pregnancy Due Date Calculator as much as you need.

How to use Pregnancy Due Date Calculator

1Choose your calculation method: LMP (first day of your last period), Conception, or IVF transfer.
2Enter the relevant date in the Date field using the calendar picker.
3For the IVF method, select the embryo age: Day 3 or Day 5 transfer.
4Optionally enter your average cycle length (in days) to refine the estimated conception date.
5Run the tool to see your estimated due date, current gestational age, trimester, and dated pregnancy milestones.

What can you do with Pregnancy Due Date Calculator?

How many weeks pregnant am i calculator — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.
Pregnancy due date by conception date — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.
How to calculate due date for ivf pregnancy — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.
What trimester am i in calculator — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.
Pregnancy week by week milestones — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.
Naegele's rule due date calculator — Free pregnancy due date calculator: enter LMP, conception, or IVF date to get your due date, gestational age, trimester, and key milestones.

Good to know

Informational only — not medical advice; confirm your dates with a doctor or midwife.
Assumes regular cycles (the 28-day default) unless you enter your own cycle length, which only refines the conception estimate.
Only about 1 in 20 babies is born on the estimated due date; a ±2-week window is normal.
IVF mode uses standard clinical offsets: Day 5 transfer +261 days, Day 3 transfer +263 days.
Milestone dates are typical timings from the engine's week table, not personalized medical guidance.

How it works

The engine is the open-source pregnancy-due-date-calculator (DarnOsint, MIT), using standard obstetric rules: Naegele's rule adds 280 days to the first day of your last menstrual period (LMP); conception-date mode adds 266 days; IVF mode adds 261 days after a Day 5 transfer or 263 days after a Day 3 transfer. Gestational age is the whole days between the LMP-equivalent date and today, expressed as weeks plus days; trimesters follow the 1–13 / 14–26 / 27–40 week bands; the 12 dated milestones come from the engine's week table (heartbeat around week 6, anatomy scan around weeks 18–20, viability at week 24, full term at week 37). If you enter a cycle length, the estimated conception date shifts to LMP + (cycle length − 14) instead of the default 28-day assumption. Limitations: only about 1 in 20 babies arrives on the estimated due date — treat it as a ±2-week guide, not a prediction; the estimate assumes regular cycles and cannot account for individual medical factors. This is an informational estimate, not medical advice — confirm dates with your clinician.

Examples

LMP method — last period January 15, 2026

Estimated due date: October 22, 2026 — Naegele's rule adds 280 days to the first day of the last period.

Conception method — conception February 2, 2026

Estimated due date: October 26, 2026 — conception-date mode adds 266 days.

IVF Day 5 transfer — February 1, 2026

Estimated due date: October 20, 2026 — Day 5 transfers add 261 days from transfer day.

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