Pregnancy Due Date Calculator
Your estimated due date from LMP, conception or ultrasound. Free, private and instant.
How to use the Due Date Calculator
- Choose work out my due date from: Last period, Conception date or Ultrasound dating.
- Answer any extra questions that appear for your choices.
- Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.
About the Due Date Calculator
The pregnancy due date calculator estimates when your baby is due using the first day of your last period, your conception date or an ultrasound measurement. It also shows how many weeks pregnant you are today, your trimester and key dates such as the anomaly scan window and full term.
Also known as: due date calculator, EDD calculator, pregnancy calculator, when is my baby due, Naegele's rule calculator.
Worked example
Dates in this example are worked out as if today were 5 Nov 2026.
- Work out my due date from: Last period
- First day of your last period: 18 Jul 2026
- Average cycle length: 28 days
Days until your due date: 170 days (Due 24 Apr 2027). Your estimated due date is Sat, 24 Apr 2027. Today you are 15 weeks 5 days pregnant, in the second trimester.
- Estimated due date: 24 Apr 2027
- Pregnant today: 15 weeks 5 days
- Trimester: Second trimester
- Weeks to go: 24.3
Formula and cut-offs
Due date = first day of last period + 280 days (40 weeks), adjusted if your cycle is not 28 days. From conception: conception date + 266 days. From ultrasound: scan date + (280 - gestational age at scan in days).
Frequently asked questions
How is a due date calculated?
Naegele’s rule adds 280 days (40 weeks) to the first day of your last period. A 28-day cycle with ovulation on day 14 is assumed.
How accurate is a due date?
Only about 5% of babies are born on their due date. Most arrive between 37 and 41 weeks. An early ultrasound gives the most accurate date.
Why is pregnancy counted from the last period?
Because the date of conception is usually not known. Counting from the last period makes pregnancy 40 weeks, about 2 weeks longer than the baby’s true age.
If my last period started on 18 Jul 2026, when is my due date?
Your estimated due date is Sat, 24 Apr 2027. Today you are 15 weeks 5 days pregnant, in the second trimester. This example treats 5 Nov 2026 as today. Enter your own dates above for a personal result.
Sources and references
- ACOG Committee Opinion 700 - Methods for estimating the due date
- Institute of Medicine (2009) - Weight Gain During Pregnancy: Reexamining the Guidelines
- NHS - Pregnancy guide
Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.
More health calculators
- Pregnancy Week Calculator
- Pregnancy Trimester Calculator
- Pregnancy Month Calculator
- IVF Pregnancy Due Date Calculator
- Recipe Nutrition Calculator
- Target Heart Rate Calculator
- More Pregnancy calculators
- All health calculators
- Compare medicine prices in 32 countries
Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.