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Calculators / Health & fitness / Pregnancy and due-date estimate
Pregnancy and due-date estimate calculator
Estimate due date and conception date from the first day of the last menstrual period.
On this page
Estimated due date2026-10-08
Estimated conception date2026-01-15
Calculator controls
How to calculate
Estimate due date and conception date from the first day of the last menstrual period.
Estimated due date = LMP + 280 days + (cycle length − 28); estimated conception = due date − 266 days.
Worked example
First day of last menstrual period: 2026-01-01; Typical cycle length (days): 28.
Estimated due date: 2026-10-08 ; Estimated conception date: 2026-01-15 .
Assumptions and limits
Cycle variation, assisted reproduction and ultrasound dating can change clinical estimates. Use a healthcare professional’s dating assessment.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Estimate due date and conception date from the first day of the last menstrual period. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the pregnancy and due-date estimate to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| First day of last menstrual period | Enter the value in the format shown. |
| Typical cycle length (days) | Enter a number of at least 20 and no more than 45. |
Frequently asked questions
What should I check before using the pregnancy and due-date estimate result?
Cycle variation, assisted reproduction and ultrasound dating can change clinical estimates. Use a healthcare professional’s dating assessment.
Is this pregnancy and due-date estimate result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.