Pregnancy Calculator
Estimate your due date from your last period, conception date, a known due date or an ultrasound — and see your current gestational age, trimester and days to go.
Your details
How to use this calculator
1. Choose what you know
Pick a method: the first day of your last period, a conception date, a due date your provider gave you, or an ultrasound reading. The form changes to match.
2. Enter the date
Fill in the relevant date. For the LMP method you can also adjust your average cycle length — longer cycles push the due date later, shorter cycles bring it earlier.
3. Read your timeline
The big number is your estimated due date. Below it you'll see today's gestational age, which trimester you're in and roughly how many days remain.
Gestational age vs. days to go
Gestational age counts forward from the last period (so it usually runs about two weeks ahead of the actual age of the embryo). Days to go counts down to the estimated due date from today.
About pregnancy dating
How is the due date estimated?
From the last menstrual period (LMP), pregnancy is dated as 280 days (40 weeks) from the first day of your last period, adjusted for cycle length. From a known conception date it is 266 days. Ultrasound dating works backward from the measured gestational age.
How accurate is a calculated due date?
Only about one in twenty babies arrives on the exact estimated date. The estimate is a guide; an early ultrasound and your care provider give the most reliable dating.
Not medical advice
This calculator is for general information only and is not a substitute for professional care. Always confirm your dates and any concerns with your doctor or midwife.