Pregnancy Due Date Calculator
A standard pregnancy lasts approximately 280 days (40 weeks) from the first day of the last menstrual period. Enter your LMP date below to calculate your estimated due date.
In LAND mode, enter the first day of your last menstrual period as field A, set the duration to 280 days, and tap add (+). The result is your estimated due date.
Common pregnancy milestones in days:
Day 28 — first missed period
Day 42 — 6 weeks, first ultrasound often scheduled
Day 98 — end of first trimester (14 weeks)
Day 196 — end of second trimester (28 weeks)
Day 280 — estimated due date (40 weeks)
To calculate how many weeks pregnant you are, switch to SPAN mode, enter your LMP date as field A and today as field B, then tap the result to see the count in weeks.
Note: this is an estimate. Actual due dates are confirmed by ultrasound. Always consult your healthcare provider.
Frequently Asked Questions
How do I calculate my pregnancy due date?
Enter the first day of your last menstrual period in field A, set duration to 280 days, and tap add. The result is your estimated due date.
How many weeks pregnant am I?
Enter your LMP date as field A and today as field B in SPAN mode. Tap the result to see the count in weeks.
What is the 40-week pregnancy calculation based on?
The 40-week estimate is measured from the first day of the last menstrual period, which is the clinical standard used by healthcare providers worldwide.