Pregnancy Due Date Calculator

Estimate your baby's due date based on the first day of your last menstrual period and your average cycle length. Find out how far along you are and which trimester you're in.

First Day of Last Menstrual Period (LMP)

Average Cycle Length (days)

Estimated Due Date

Weeks Pregnant

Trimester

Estimated Conception

Days Remaining

This calculator provides estimates and is for informational purposes only. Consult a healthcare professional for medical advice.

How It Works

This calculator uses Naegele's Rule, the standard method used by healthcare providers. It adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle is longer or shorter than the average 28 days, the estimate is adjusted accordingly.

Conception typically occurs around day 14 of a 28-day cycle (ovulation). A full-term pregnancy lasts approximately 40 weeks from the LMP, or about 38 weeks from conception. Only about 5% of babies are born on their exact due date — most arrive within a two-week window around it.

Frequently Asked Questions

How accurate is the due date calculation?

Naegele's Rule provides a good estimate, but only about 5% of babies arrive on the exact due date. Most births occur between 38 and 42 weeks. An ultrasound in the first trimester can provide a more precise estimate.

What if I don't know my cycle length?

If you're unsure of your average cycle length, use the default of 28 days. This is the most common cycle length and will give a standard estimate. Your doctor can refine this with an ultrasound.

When does each trimester start and end?

The first trimester spans weeks 1–12, the second trimester covers weeks 13–26, and the third trimester runs from week 27 until delivery (around week 40). Each trimester brings different developmental milestones.

Pregnancy Due Date Calculator

How It Works

Frequently Asked Questions

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