Due Date Calculator: The Complete Guide
Estimate when your baby is due. Enter the first day of your last period to get your estimated due date using Naegele's rule, along with your estimated conception date and trimester milestones.
Who the Due Date Calculator is for
Expectant parents who want their estimated due date and key pregnancy milestone dates.
How to use the Due Date Calculator
- Type your values into the fields above — pick your currency or units where the calculator offers them.
- Results update automatically as you type; there's no submit button and nothing is sent to a server.
- Adjust any input to compare scenarios, then copy the result with a single click.
How it works
Naegele's rule estimates the due date as the first day of the last period plus 280 days (40 weeks), assuming a regular 28-day cycle. Conception is estimated around day 14.
Features
- Estimated due date
- Estimated conception date
- Trimester milestones
- Instant result
How the due date is estimated
Naegele's rule — last period plus 280 days — is the standard way to estimate a due date. It assumes a 28-day cycle with ovulation on day 14, so if your cycle is longer or shorter the date shifts. A first-trimester ultrasound gives the most accurate dating and may adjust this estimate.