Free tool
Due date calculator
Enter the first day of your last period or your conception date: get your estimated due date, how far along you are, and the key dates of all three trimesters.
Calculate my due date
Estimated due date
Free, no sign-up. What you enter stays in your browser: nothing is sent to Maliah.
How the due date is calculated
The estimated due date is counted from the first day of your last menstrual period: add 280 days, or 40 weeks. This is Naegele’s rule, the one most professionals use. If your cycle is longer or shorter than 28 days, the tool shifts the date accordingly. If you know the conception date, it adds 266 days to it.
An “estimated” date, not a fixed one
Few babies are born on their exact due date: most arrive in the weeks around it. The first-trimester ultrasound often refines it; the date your health professional gives you is the one that counts.
Weeks of pregnancy
Weeks are also counted from the first day of your last period, so about two weeks before conception. Pregnancy is often split into three trimesters: the first until the end of week 13, the second until week 27, the third until birth.
Following your pregnancy day to day
In Maliah, the pregnancy has its own profile: current week, appointments, questions for the next visit, hospital bag and birth plan, shared with your partner. In Québec, the “Ma grossesse” service on Québec.ca helps you find a professional for prenatal care.
Frequently asked questions
How do I calculate my due date?
Add 280 days (40 weeks) to the first day of your last period, adjusting if your cycle isn’t 28 days. From a conception date, add 266 days.
My ultrasound gives a different date: which one is right?
The date from the first-trimester ultrasound is usually more precise. Follow the one your health professional gives you.
How many weeks pregnant am I?
The tool counts weeks from the first day of your last period, like professionals do: you see the current week and days.
When does each trimester start?
The first trimester runs to the end of week 13, the second to week 27, and the third from week 28 until birth.
Is my data sent anywhere?
No. The calculation happens in your browser; nothing is sent to Maliah or saved.
Sources : Naître et grandir : calculer sa date d’accouchement · Québec.ca : service Ma grossesse
This tool is for information only; it does not replace advice from a health professional or an official body. If you have a health concern, call Info-Santé 811. In an emergency, dial 911. Updated October 24, 2026.