How is the due date calculated?

The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is called Naegele's rule and is the standard method used by doctors worldwide.

How many weeks is a full-term pregnancy?

A full-term pregnancy is 40 weeks (280 days) from the first day of the last menstrual period. Babies born between 39 and 40 weeks are considered full term. Most pregnancies last between 38 and 42 weeks.

What are the three trimesters of pregnancy?

The first trimester is weeks 1-12, the second trimester is weeks 13-26, and the third trimester is weeks 27-40. Each trimester involves distinct developmental milestones for the baby.

Pregnancy Calculator

Calculate your due date, current pregnancy week, trimester and days remaining. Enter your last period date or conception date. Free, no signup required.

Free No Signup Due Date Week by Week

Pregnancy Calculator

First day of last period

Average cycle length

days (default 28)

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Enter your details and tap
Calculate Due Date

Free Pregnancy Due Date Calculator

Our pregnancy calculator uses the standard Naegele's Rule — adding 280 days (40 weeks) to the first day of your last menstrual period — to estimate your due date. You can also enter your conception date directly for IVF pregnancies or when you know your exact ovulation date.

The calculator shows your current pregnancy week, trimester, days remaining and a visual progress bar from Week 1 to Week 40. Key milestones like the first ultrasound window, anatomy scan and third trimester start are also shown so you know what to expect and when.

Pregnancy Week by Trimester

Trimester	Weeks	Key Development
First Trimester	Weeks 1–12	Baby's heart starts beating (week 6), all organs form, risk of miscarriage highest
Second Trimester	Weeks 13–26	Baby moves, gender visible, anatomy scan at week 20, most comfortable trimester
Third Trimester	Weeks 27–40	Baby gains weight, brain develops, lungs mature, kicks felt regularly

Frequently Asked Questions

How accurate is the due date calculator?

Due dates calculated from the last menstrual period are accurate to within 1–2 weeks. Only about 4% of babies are born on their exact due date. Your doctor will confirm your due date with an ultrasound in the first trimester, which is more accurate.

What if my cycle is not 28 days?

Enter your actual cycle length in the Cycle Length field. Our calculator adjusts the due date accordingly. Cycles shorter than 28 days mean an earlier ovulation date, while longer cycles mean a later ovulation — both affect the estimated due date.

When should I take a pregnancy test?

A home pregnancy test can detect pregnancy from the first day of a missed period — usually about 14 days after conception. Some sensitive tests can detect it even earlier. For most accurate results, test in the morning with your first urine of the day.

Is this pregnancy calculator free?

Yes, 100% free. No account required. This tool is for informational purposes only — always consult your doctor or gynaecologist for medical advice.