How to Use This Due Date Calculator
Our free due date calculator gives you accurate estimates in seconds. Enter your numbers above and hit Calculate — results update instantly.
All calculations use current 2026 rates and formulas. Results are estimates to help you plan — always verify with a licensed professional for final numbers.
Frequently Asked Questions
How is my due date calculated?
Your due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This is called Naegele rule and is the standard method used by doctors worldwide.
How accurate is a due date calculator?
Due date calculators give an estimated due date. Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the estimated date.
Can I calculate due date by conception date?
Yes. If you know your conception date, add 266 days (38 weeks) to get your estimated due date. This method can be more accurate if you tracked ovulation.
What is a full-term pregnancy?
A full-term pregnancy is 39-40 weeks. Early term is 37-38 weeks, late term is 41 weeks, and post-term is 42 weeks or beyond.
How do I count pregnancy weeks?
Pregnancy weeks are counted from the first day of your last menstrual period. At conception, you are considered 2 weeks pregnant. A full-term pregnancy is 40 weeks.