🤰 Calculators & Daily Life

Pregnancy Due Date Calculator

Estimate your due date, and how many weeks pregnant you are today, from your last menstrual period (or conception / ovulation date), along with the pregnancy month and trimester. Everything is calculated in your browser and the dates you enter never leave it. This is an estimate based on Naegele's rule, not medical advice.

Examples (click to try)

Enter the date matching the "Reference type" you pick on the right.

Usually 28. If yours differs, the due date is shifted by the difference from 28 days (last menstrual period mode only).

⚠️ This tool is an estimate based on Naegele's rule, not medical advice. Always confirm your actual due date and the progress of your pregnancy with a clinic.

How to use the pregnancy due date calculator

Enter a date in "Reference date", choose whether it is your last menstrual period, conception date or ovulation date in "Reference type", and the estimated due date plus how many weeks pregnant you are today, the pregnancy month and the trimester appear instantly. It recalculates whenever you change a value.

  • Last menstrual period (LMP): the most common reference. The due date is the first day of your last period plus 280 days (40 weeks).
  • Conception / ovulation date: these occur roughly two weeks after the last period, so 266 days are added to reach the due date.
  • Cycle length: used only in last-menstrual-period mode. If it differs from 28, the due date is shifted by that difference (a longer cycle pushes the due date later, a shorter one earlier).
  • Pregnancy weeks: counted from the first day of the last menstrual period as "0 weeks 0 days". The due date is exactly 40 weeks 0 days. The month shown is a 4-week (lunar) month.

Handy for

  • Getting a rough estimate of your due date
  • Quickly checking "how many weeks and days pregnant am I now?"
  • Seeing the approximate pregnancy month and trimester (1st–3rd)
  • Seeing how a cycle other than 28 days shifts the due date

Medical note: This tool is an estimate based on Naegele's rule, not a medical diagnosis or advice. Your actual due date is determined by a clinic, for example from an ultrasound scan. If you have any concerns about the progress of your pregnancy or your health, do not rely on this tool alone — please consult an obstetrician or other clinic.

FAQ

Are the dates I enter sent to a server?
No. Everything is calculated entirely in your browser, and the dates or cycle length you enter are never transmitted to or stored on any server. Because pregnancy information is highly sensitive, it stays on your device.
How is the due date calculated?
It uses Naegele's rule, adding 280 days (40 weeks) to the first day of your last menstrual period. If you pick a conception or ovulation date it adds 266 days instead, and a cycle length other than 28 days shifts the result by the difference from 28 days. This is only an estimate; your real due date is determined by a clinic, for example from an ultrasound scan.
How are the pregnancy weeks counted?
The first day of the last menstrual period counts as week 0, day 0, and the due date falls at 40 weeks 0 days. Conception and ovulation happen at roughly the 2-week mark, so when you calculate from those dates the 0-week origin is converted back to the equivalent last-period day.