Pregnancy Due Date Calculator
Estimate your due date and current week, with saved dates and week-by-week tips and cautions.
Pick a date to estimate the due date.
Estimates use Naegele's rule (due date = last period + 280 days, adjusted for cycle length). Only about 1 in 20 babies arrives on the exact due date, and an ultrasound gives a more accurate estimate. This tool is for general information and is not medical advice — always follow your doctor or midwife.
Use on any page (bookmarklet)
Want Pregnancy Due Date Calculator without leaving the page you're on? Drag the button below to your bookmarks bar, then click it on any website to open Pregnancy Due Date Calculator right there — it runs entirely in your browser.
Use responsibly: a bookmarklet runs on whatever page you click it on. Avoid sensitive sites such as online banking, payment, or healthcare pages — you run it at your own risk. Everything is processed locally and no data is sent anywhere. See our Terms.
- Show your bookmarks bar if it's hidden — Ctrl+Shift+B (⌘+Shift+B on Mac).
- Drag the button above onto the bookmarks bar.
- Open any website and click the bookmark — the Pregnancy Due Date Calculator panel appears in the top-right corner. Use ✛ to move it between corners, or ›/‹ to tuck it against the edge and pull it back out.
- Click the bookmark again (or the ✕) to close it.
Note: a few sites with strict security policies may block bookmarklets.
Examples
From last period
Input
LMP Jan 1 · 28-day cycle
Output
Due ~Oct 8 (280 days later)
From conception
Input
Conception Jan 15
Output
Due ~Oct 8 (266 days later)
Longer cycle
Input
LMP Jan 1 · 32-day cycle
Output
Due date shifts ~4 days later
About this tool
This free pregnancy due date calculator estimates when your baby is due and how far along you are right now. Enter the first day of your last period — or a conception date, or a due date you already know — and it works out the estimated due date, your current week and day, the trimester, and how many days are left.
How to use
- Choose what you know: last period, conception date, or due date.
- Pick the date.
- If using your last period, set your average cycle length.
- Read your estimated due date and how far along you are.
An estimate, not a diagnosis
Due dates are estimates — babies come when they're ready, usually within a week or two of the date. An ultrasound dating scan is more precise, particularly with irregular cycles. Use this as a friendly guide and always follow your healthcare provider for medical care.
Frequently asked questions
How is the due date calculated?
The tool uses Naegele's rule: it adds 280 days (40 weeks) to the first day of your last menstrual period (LMP), adjusted for your cycle length. If you enter a conception date instead, it adds 266 days; if you already know your due date, it works the dates backward from there.
How accurate is the estimated due date?
It's an estimate. Only about 4–5% of babies are born on their exact due date — most arrive within a week either side. An early ultrasound (dating scan) is the most accurate way to estimate the due date, especially if your cycle is irregular.
What if my cycle isn't 28 days?
Enter your actual average cycle length. Ovulation usually happens about 14 days before your next period, so a longer or shorter cycle shifts the due date. The calculator adjusts the LMP-based estimate by the difference from 28 days.
How many weeks pregnant am I?
Pregnancy is counted in weeks from the first day of your last period, not from conception — which is why you're considered about 2 weeks pregnant at the moment of conception. The tool shows your current weeks and days along, plus which trimester you're in.
When do the trimesters start and end?
Roughly: the first trimester is weeks 1–13, the second is weeks 14–27, and the third is weeks 28 to birth (around week 40). The tool labels your current trimester based on how far along you are.
Does it show tips for each stage of pregnancy?
Yes. Once you enter a date, the tool shows a card for your current week — what's generally happening at that stage, things to take care with, and helpful tips — updated as you move through each trimester. It's general information, not personal medical advice.
Does it remember my date so I don't re-enter it?
Yes. Your entry (the date, method, and cycle length) is saved in your browser, so when you come back the calculator shows your current week and stage tips right away. It's stored only on your device — nothing is uploaded. We never ask for a name or the baby's sex.
Is this a substitute for medical care?
No. This is a general-information estimate only, not medical advice. Always confirm dates and get care from your doctor, midwife, or a qualified healthcare provider.
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