TheFreeTool

Due Date Calculator

Enter the first day of your last period and the usual length of your cycle. The calculator estimates your due date, how far along you are and when you probably conceived.

Good to know

This tool gives general information only and is not medical advice. Only a healthcare professional can confirm a pregnancy and its due date.

What it does

  • Due date from your last period
  • Adjusted for your cycle length
  • Weeks and days pregnant, and the trimester
  • Estimated conception date

How to use it

  1. Enter the first day of your last period.
  2. Enter your usual cycle length in days. 28 is the average.
  3. Read your due date, how many weeks pregnant you are and the conception date.

How is the due date worked out?

The standard method, Naegele's rule, counts 280 days (40 weeks) from the first day of your last period. If your cycle is longer or shorter than 28 days, the date moves later or earlier by the difference. Conception is usually estimated at about 14 days into a 28-day cycle.

Only about 5 in 100 babies arrive on the due date. Most arrive within two weeks either side. An early ultrasound can give a more accurate date, so your midwife or doctor may adjust it.

Example

If your last period started on 1 March 2026 and your cycle is 28 days, your due date is Sunday, 6 December 2026. You would have conceived around 15 March.

Questions people ask

How accurate is a due date?
It is an estimate. Only a small share of babies are born on the day. Most arrive in the two weeks either side.
What if my cycle is irregular?
The date may be off. Your doctor or midwife can use an early ultrasound to confirm it.
Is this medical advice?
No. It is general information. Always follow the advice of your own healthcare team.

Disclaimer

This tool is for general information only and is not medical advice. Results are estimates and do not diagnose, treat or replace a doctor, dietitian or other health professional. Talk to a qualified professional before you change your diet, exercise or health routine. You use this tool at your own risk, and TheFreeTool is not liable for any loss or harm that follows. Read the full disclaimer

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