Estimate your due date from your last period, conception date, or IVF transfer.
Updated Sep 2026Fill in the fields and press Calculate. Every range comes from the sources listed under the tool.
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This tool is for general information only and is not medical advice. Talk to a healthcare professional about results that concern you.
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Sources
- Methods for Estimating the Due Date (Committee Opinion No. 700) ACOG
- Estimated Date of Delivery - StatPearls - NCBI Bookshelf NIH / NCBI Bookshelf (StatPearls)
- Pregnancy Dating - StatPearls - NCBI Bookshelf NIH / NCBI Bookshelf (StatPearls)
- Gestational age: MedlinePlus Medical Encyclopedia MedlinePlus (NIH National Library of Medicine)
How Your Due Date Is Calculated
Pregnancy lasts about 40 weeks counted from the first day of your last menstrual period (LMP), or 38 weeks from conception. This calculator supports three methods, so you can use whichever date you know:
- Last period: the standard clinical approach (Naegele’s rule) adds 280 days to your LMP. If your cycles run longer or shorter than 28 days, the calculator shifts the date accordingly.
- Conception date: if you know the day you conceived, the estimate is that date plus 266 days.
- IVF transfer: the most precise method of all. A day 5 embryo transfer adds 261 days; a day 3 transfer adds 263.
Along with your due date, the results show how far along you are today, when each trimester begins, your full term window, and a couple of fun extras like your baby’s likely zodiac sign and birthstone.
How Accurate Is a Due Date?
A due date is an estimate, not an appointment. Only about 4 to 5 percent of babies arrive exactly on it, while roughly 90 percent are born within two weeks either side. Your provider may also adjust the date after a first trimester ultrasound, which measures the baby directly and is the most accurate dating method in early pregnancy.
Trying to conceive rather than already expecting? Our ovulation calculator finds your fertile window, and once you are pregnant the pregnancy weight gain calculator keeps your progress in a healthy range.
Frequently Asked Questions
Can my due date change?
Yes. If an early ultrasound shows the baby measuring larger or smaller than the LMP date suggests, your provider will usually re-date the pregnancy from the scan. This is common with irregular cycles.
What if I do not remember my last period?
Estimate as closely as you can, then rely on your dating ultrasound for the accurate answer. If you know roughly when you conceived, use the conception method instead.
What does full term mean?
39 weeks 0 days through 40 weeks 6 days. Early term is 37 to 38 weeks, late term is 41, and post term is 42 onward. Babies born in the full term window have the best outcomes on average.
How many weeks pregnant am I?
Enter your dates above and the result shows your exact gestational age today in weeks and days, plus which trimester you are in.
Sources
- Methods for Estimating the Due Date (Committee Opinion No. 700) · ACOG
- Estimated Date of Delivery – StatPearls – NCBI Bookshelf · NIH / NCBI Bookshelf (StatPearls)
- Pregnancy Dating – StatPearls – NCBI Bookshelf · NIH / NCBI Bookshelf (StatPearls)
- Gestational age: MedlinePlus Medical Encyclopedia · MedlinePlus (NIH National Library of Medicine)
This calculator is for general information only and is not a substitute for prenatal care. Always confirm dates with your healthcare provider.