This estimate uses Naegele’s rule (280 days from the last menstrual period). Change the date or your cycle length above, or open the full due date calculator to calculate from a known due date or conception date instead.
Due date if your last period was Wednesday, March 18, 2026
If the first day of your last period was Wednesday, March 18, 2026, your estimated due date is Wednesday, December 23, 2026 — 40 weeks later. That is about 13 weeks pregnant, with 189 days to go.
First day of your last menstrual period (how doctors date a pregnancy)
⚕️ This is an estimate based on Naegele’s rule (40 weeks from your last period). Only about 1 in 20 babies arrive on the exact due date. Always confirm with your doctor or midwife.
FAQ
What is my due date if my last period was Wednesday, March 18, 2026?
Counting 40 weeks (280 days) from Wednesday, March 18, 2026, your estimated due date is Wednesday, December 23, 2026. This assumes a 28-day cycle — adjust your cycle length in the calculator if it differs.
How many weeks pregnant does that make me?
As of today, that is about 13 weeks — trimester 1.
How accurate is this estimate?
It is an estimate — only about 1 in 20 babies arrive on the exact due date. Confirm with your doctor or midwife and an early scan.
Medical disclaimer. Estimates only, not medical advice — always confirm your due date with a healthcare professional.