Pregnancy Due Date Calculator
Estimate your due date and current week of pregnancy.
đ Runs entirely in your browser â nothing is uploaded.
âšī¸ Uses Naegele's rule (LMP + 280 days) - an estimate only. Your healthcare provider's estimate, especially from an ultrasound, is more accurate.
How Pregnancy Due Date Calculator works
How is the due date calculated?
It applies Naegele's rule: adding 280 days, or 40 weeks, to the first day of your last menstrual period. From that same starting date it also works out how many weeks pregnant you currently are and which trimester that falls into, using week 13 and week 27 as the cutoffs.
When is this calculator useful?
It's a quick way to get a working due date and current week as soon as you know when your last period started, well before a dating ultrasound is available. Many people use it early on to plan appointments or just get a rough sense of timeline.
How reliable is a due date calculated this way?
Naegele's rule assumes a regular 28-day cycle with ovulation around day 14, which doesn't hold for everyone, so actual delivery commonly falls within a couple of weeks of this estimate in either direction. This is not medical advice - an ultrasound-based estimate from a healthcare provider is more accurate and should take precedence over this calculation.