Estimate your due date & how many weeks pregnant you are
Use the FIRST day of bleeding, not the last.
Default 28. Adjusts ovulation timing.
The day of fertilization or tracked ovulation.
The day the embryo was transferred (not retrieval).
From your provider or ultrasound.
Only change this to see how far along you'd be on a different date.
Estimated due date
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This is an estimate, not medical advice. Only about 4–5% of babies arrive on their exact due date and most come within about two weeks either side. A first-trimester ultrasound is the most accurate way to date a pregnancy — always confirm your due date with your healthcare provider.
Due Date Calculator — guide & how to use
What it does
The Pregnancy Due Date Calculator estimates your estimated due date (EDD) and tells you
how many weeks pregnant you are right now. It works from your last menstrual period,
a known conception/ovulation date, or an IVF embryo transfer — and can reverse a due date you already
have back into your LMP and conception date. It also shows your current trimester,
estimated conception date, days remaining, and key pregnancy milestones —
all calculated privately in your browser, free.
How to use it
Pick how you want to calculate from — LMP is the clinical default.
Enter the required date (and your cycle length for LMP, or the embryo age for IVF).
Read your estimated due date, how far along you are in weeks + days, your trimester, and your milestone dates.
How the math works
LMP (Naegele's rule): EDD = LMP + 280 days (40 weeks), shifted by (cycle length − 28) days when your cycle isn't 28.
Conception / ovulation: EDD = conception date + 266 days.
IVF transfer: EDD = transfer date + (266 − embryo age). Day 3 → +263, Day 5 → +261, Day 6 → +260, Day 7 → +259.
Weeks pregnant is counted from the LMP (or the equivalent LMP origin), so it includes roughly two weeks before conception — this is normal clinical convention.
Accuracy & safety notes
This tool is an estimate for planning only and does not replace prenatal care or an ultrasound-confirmed due date.
Only ~4–5% of babies are born on the exact EDD; ~80–90% arrive within about ±2 weeks. Treat the EDD as a midpoint, not a deadline.
Naegele's rule assumes a regular 28-day cycle with ovulation on day 14 — less reliable for irregular cycles or uncertain LMP.
An accurately measured first-trimester ultrasound (±5–7 days) is more accurate than LMP dating (±1–2 weeks). If they disagree by more than 5–7 days, providers generally use the ultrasound date.
For IVF pregnancies, the embryo-transfer date is used (not LMP), per ACOG guidance.
Term definitions (ACOG): early term 37w0d–38w6d, full term 39w0d–40w6d, late term 41w0d–41w6d, post-term ≥42w0d.
For twins or higher multiples the EDD still reflects the singleton 40-week convention, but multiples are typically delivered earlier (often 35–37 weeks for twins).
All computation is client-side — no health data leaves your device.
Frequently asked questions
How is the due date calculated?
Naegele's rule: EDD = first day of your last period + 280 days, adjusted by (cycle length − 28) days. From conception it's +266 days; for IVF it's transfer date + (266 − embryo age).
How accurate is it?
Only ~4–5% of babies arrive on the exact date; ~80–90% come within about two weeks of it. A first-trimester ultrasound is the most accurate method — confirm with your provider.
Why does it say I'm "pregnant" before conception?
Gestational age is counted from your last period by convention, so weeks 1–2 are before conception actually happens. This is expected, not an error.
Is it really free?
Yes. 100% free, everything runs privately in your browser.
No account, no coding. Copy the embed code and paste it where you want it to appear:
<iframe src="https://snaptoolsuite.com/due-date-calculator/?embed=1"
style="width:100%;max-width:560px;height:1000px;border:0;"
title="Pregnancy Due Date Calculator" loading="lazy"></iframe>
<p>Free <a href="https://snaptoolsuite.com/due-date-calculator/">Due Date Calculator</a> by Snap Tool Suite</p>