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Due Date Calculator

Calculate your estimated due date from your last menstrual period or conception date, with current pregnancy week, trimester, and key milestones.

Last updated: 2026/10/16 Calculator Feedback & bug reports
This tool provides a general estimate based on Naegele's rule (last menstrual period + 280 days). It is not medical advice. Always consult your doctor or midwife regarding your actual due date and pregnancy progress.
Input
days
Standard is 28 days. Adjust if your cycle is longer or shorter.
The date used to calculate the current pregnancy week.
Enter a date to see your due date and current pregnancy week.

How to Use

1

Choose a method and date

Select "From last menstrual period" or "From conception / ovulation" and enter the relevant date. Using the LMP is the most common and convenient option.

2

Adjust cycle and reference date (optional)

If your cycle differs from 28 days, enter it to fine-tune the due date. Leave the reference date as today to get your current pregnancy week automatically.

3

Review results and milestones

See your due date, pregnancy week, trimester, and milestones such as the stable period and full-term. Use "Copy Results" to paste into notes or messages.

About the Due Date Calculator

A web tool that estimates your due date from your last menstrual period (LMP) or conception/ovulation date using Naegele's rule (LMP + 280 days = 40 weeks 0 days). It shows your current pregnancy week, month, and trimester, plus milestones such as the likely heartbeat, the stable period, and full-term. All calculations run entirely in your browser, so the dates you enter are never sent to any server. This tool provides a general estimate only and is not a substitute for medical advice.

Features

  • Real-time CalculationEnter a date and instantly see your due date and pregnancy week. No buttons to press.
  • Rich MetricsPregnancy week, trimester, month, progress, and estimated conception date in one view.
  • Milestones & Japanese EraKey dates like the stable period and full-term, with the due date also shown in the Japanese era.
  • Privacy ProtectedAll processing happens in your browser. The data you enter is never sent to servers.

Use Cases

  • Get an approximate due date when you find out you are pregnant
  • Check how many weeks, months, or which trimester you are currently in
  • Anticipate when the stable period and full-term will begin
  • Plan maternity leave and travel schedules
  • Map out upcoming checkups and prenatal classes

FAQ

How is the due date calculated?
It uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). When calculating from a conception/ovulation date, 266 days (38 weeks) are added. This assumes a 28-day cycle with ovulation on day 14 and is a general estimate.
What if my cycle is not 28 days?
Enter your actual cycle length and the tool adjusts the due date by the difference from 28 days. For example, a 32-day cycle shifts the due date about 4 days later. For irregular cycles, your doctor's ultrasound-based date takes priority.
How are pregnancy weeks counted?
Pregnancy weeks are counted from the first day of your last menstrual period as "week 0, day 0", so counting starts before conception and implantation. This tool computes your current "week X day Y" from the days up to the reference date (usually today).
What are full-term and the stable period?
Full-term is weeks 37 0/7 to 41 6/7, and birth during this window is considered term birth. The stable period generally refers to roughly week 16 (month 5) onward, when miscarriage risk decreases and symptoms often ease. Both vary by individual and are estimates only.
Are the dates I enter saved?
No. All calculations happen entirely in your browser, and the dates you enter are never sent to or stored on any server, so you can use the tool with peace of mind.
Is this result accurate? Can it be used for medical purposes?
The result is a general estimate, not medical advice. Your actual due date is determined more accurately by ultrasound (especially early-pregnancy fetal measurements). Always consult your doctor or midwife about your pregnancy and due date.

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Related Guides

Due Date Calculation and Counting Pregnancy Weeks (Naegele Rule) A clear guide to calculating the due date with Naegele's rule and counting pregnancy weeks, months, and trimesters from the last period, plus why the due date is only an estimate. Not medical advice.