Pregnancy Week Calculator
Estimate your due date, gestational age in weeks and days, trimester, and days remaining from your last menstrual period. Free and instant.
Independently verified for accuracy
Calculator by Toolsloft ↗- Estimated due date
- 2026-10-08
- Gestational age
- 25 weeks 2 days
- Trimester
- 2
- Days remaining
- 103
Estimate your due date, how far along you are in weeks and days, your current trimester, and the days left until your estimated due date. Enter the first day of your last menstrual period and the date you want the estimate calculated for.
How this is calculated
Due date follows Naegele's rule, where the estimated due date equals the first day of the last menstrual period plus 280 days (40 weeks). Gestational age is the number of days from that first day to the as-of date, expressed as completed weeks and remaining days, and the trimester is read from the completed weeks. This is an informational estimate, not medical advice; talk to a clinician for care decisions.
How to use
- Enter the first day of your last menstrual period.
- Enter the date you want the estimate calculated for.
- Read your estimated due date, gestational age, trimester, and days remaining.
Examples
- Last period 2026-01-01, as of 2026-06-27:
Due 2026-10-08, 25 weeks 2 days, trimester 2 - Last period 2025-12-15, as of 2026-06-27:
Due 2026-09-21, 27 weeks 5 days, trimester 3
FAQ
- How is the due date calculated?
- The due date uses Naegele's rule: the first day of your last menstrual period plus 280 days, which is 40 weeks.
- What is gestational age?
- Gestational age is how far along the pregnancy is, measured from the first day of the last menstrual period. It is shown here as completed weeks plus the leftover days.
- Is this a substitute for an ultrasound dating scan?
- No. This is an informational estimate based on cycle dates. An ultrasound scan and your clinician give a more precise assessment.