Health & FitnessReviewed Methodology
Pregnancy Due Date Calculator
This pregnancy due date calculator tool helps you estimate an expected delivery date by using the first day of your last menstrual period.
Quick answer
Uses a standard 280-day gestational estimate dated from LMP.
What this tells you
- •Uses a standard 280-day gestational estimate dated from LMP.
- •Also shows estimated conception date.
- •Results are planning estimates and can vary.
How to Use
- 1Enter the first day of your last menstrual period.
- 2Calculate to see estimated conception and due date.
- 3Use results as a guide and confirm with a healthcare provider.
How It Works
Formula
Due Date = LMP + 280 daysThis follows Naegele-style due date estimation from last menstrual period.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
LMP example
L M P2026-01-01
ResultEstimated due date: 2026-10-08
Common mistakes
- Using an uncertain LMP date
- Treating estimate as exact delivery date
- Ignoring cycle irregularity impacts
Limitations
This estimate assumes LMP-based dating and a typical 280-day gestation pattern. Clinical dating can differ due to irregular cycles, uncertain LMP recall, ovulation timing variation, implantation timing, and ultrasound findings.
Frequently Asked Questions
No. It is an estimate based on a standard gestation model.
Irregular cycles can reduce estimate accuracy.
Yes. Clinical assessment is important for accurate pregnancy dating.
Use the Health category hub at /health/ for related non-diagnostic planning tools.