Health & Fitness
Due Date Calculator
Estimate pregnancy due date based on last menstrual period and cycle length.
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
How is the due date calculated?
It uses a standard 40-week estimate adjusted by cycle length.
Is the due date exact?
No. It is an estimate and actual delivery may vary.
Can I use irregular cycles?
Use your best estimate for cycle length. Results may be less accurate.
Related tools
About this tool
Inputs
- First day of last period
- Cycle length
Results
- Estimated due date
- Weeks pregnant
Figuring out estimate pregnancy due date based on last menstrual period and cycle length no longer requires manual arithmetic. The Due Date Calculator walks you through the math step by step. You supply first day of last period and cycle length, and the tool calculates estimated due date and weeks pregnant from those figures. Tracking health indicators over time reveals trends that one-off measurements miss. Body fat percentage formulas rely on skinfold measurements or circumference-based estimates, each with its own margin of error.
Whether you need to estimate pregnancy due date based on last menstrual period and cycle length for a quick check or a thorough analysis, this tool adapts to both. Age, sex, ethnicity, and fitness level all influence what counts as a healthy range for you. Use your best estimate for cycle length. Results may be less accurate. Change one variable while holding the others constant to isolate its impact. This sensitivity check is often more informative than a single result.