Due Date Calculator
Estimate your pregnancy due date, current week and trimester from the first day of your last period.
About this calculator
This free due date calculator estimates when your baby is likely to arrive, how far along you are right now, and which trimester you are in — all from the first day of your last menstrual period (LMP).
How it works
Pregnancy typically lasts about 40 weeks (280 days) from the LMP. The calculator adds 280 days to your LMP and adjusts for your cycle length, so the estimate fits your body rather than a fixed 28-day assumption.
Trimesters
- First trimester: weeks 1–12
- Second trimester: weeks 13–26
- Third trimester: weeks 27–birth
Planning ahead or trying to conceive? The ovulation calculator estimates your fertile window, and the age calculator works out an exact age once your baby arrives.
Frequently asked questions
It uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your cycle length. This is the same method most doctors use for a first estimate.
It is an estimate. Only about 1 in 20 babies is born on the exact due date; most arrive within two weeks either side. A dating ultrasound gives a more precise estimate.
Enter your average cycle length and the calculator shifts the due date accordingly — longer cycles push the due date later, shorter cycles bring it earlier.
Pregnancy is counted from the first day of your last period, not from conception, so you are already considered about two weeks pregnant at conception. The calculator shows your current week and day.
Completely. The dates you enter are processed only in your browser and are never uploaded or stored.
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