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Pregnancy Due Date Calculator

Estimate your due date from your last menstrual period.

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About Health Calculator

BMI is a population screening figure and carries no information about body composition, so it misreads muscular and older bodies in opposite directions. All three outputs are estimates for planning, not a substitute for a clinician.

Estimate a pregnancy due date and approximate conception date from the first day of your last period. This is an informational estimate calculated in your browser — always confirm with a clinician.

Estimate your Body Mass Index, daily calorie needs using the proven Mifflin–St Jeor formula, and a pregnancy due date from your last menstrual period. It brings three common health estimates together so you can plan diet, fitness and milestones quickly.

These figures are informational estimates rather than medical advice — take decisions about your health with a clinician. Calorie targets especially are a starting point to adjust against real results, since activity level is self-reported and easy to overstate.

Learn how this works

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Frequently asked questions

How is the due date worked out?

By Naegele's rule: 280 days — 40 weeks — from the first day of your last menstrual period. It assumes a regular 28-day cycle with ovulation around day 14, which is why a dating scan is more accurate for anyone whose cycle differs.

How likely am I to give birth on the due date itself?

Only around 4% of births happen on the estimated date. It marks the middle of a normal range, not a deadline — most births occur within roughly two weeks either side.

Should I rely on this instead of a scan?

No. This is an estimate for general information only. An early ultrasound measures the baby directly and is what clinicians use to set the official date. Always follow the guidance of your midwife or doctor.

Common Use Cases

  • •Getting an early estimate before a first midwife appointment
  • •Working out roughly which trimester a given week falls in
  • •Planning leave dates around an approximate window

More Health Calculator tools

Health CalculatorBMI CalculatorCalorie Calculator (BMR & TDEE)

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