Health
Pregnancy Due Date
Illustrate an estimated due date, trimester and elapsed calendar weeks from LMP only. Not clinical pregnancy dating.
Guide
How to use the Pregnancy Due Date
The Pregnancy Due Date helps you make a quick estimate, compare scenarios, and understand the numbers behind the result. It is designed for fast planning, with enough context to make the answer useful instead of just a number.
- Enter current measurements as accurately as possible, using the unit system that fits you best.
- Read the equation, reference assumptions and limitations alongside the estimate.
- Adjust assumptions such as activity level, sex, age, or goal where the calculator supports them.
Method
How this calculator works
It adds 280 calendar days to LMP and counts completed calendar weeks and remaining days. It assumes a 28-day cycle with ovulation around day 14; no conception-date, IVF, cycle-length or ultrasound inputs are supported.
This calculator is useful for a calendar illustration of estimated due date and elapsed weeks, not clinical dating or a prenatal care schedule.
Because assumptions matter, try a few values that represent optimistic, typical, and conservative cases.
Health calculators are screening and planning tools, not medical advice. They cannot replace a clinician's evaluation.
Example
Worked example
LMP November 10, 2025 plus 280 calendar days gives August 17, 2026. On January 19, 2026, that calendar count is 10 completed weeks and 0 days, with 210 days to the estimate. Daylight-saving changes do not alter these calendar dates.
FAQ
Common questions
How is this estimated due date calculated?
The tool adds 280 calendar days to the first day of the last menstrual period. It assumes a 28-day cycle; actual timing and clinical dating can differ.
Is 37 weeks full term?
No. NICHD defines early term as 37 weeks through 38 weeks and 6 days, and full term as 39 weeks through 40 weeks and 6 days.
Can it date an IVF pregnancy or use ultrasound results?
No. This tool has only an LMP input. Use the date established by your clinician for clinical decisions, including assisted reproduction or uncertain cycles.
What information do I need for the Pregnancy Due Date?
You usually need the first day of the last menstrual period (LMP), within the tool's one-year calendar range. You can change the inputs and recalculate as many times as needed.
How does the Pregnancy Due Date calculate the result?
It adds 280 calendar days to LMP and counts completed calendar weeks and remaining days. It assumes a 28-day cycle with ovulation around day 14; no conception-date, IVF, cycle-length or ultrasound inputs are supported.
Are the results exact?
Health calculators are screening and planning tools, not medical advice. They cannot replace a clinician's evaluation.
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