Financial CalculatorsFitness & Health CalculatorsMath CalculatorsOther Calculators All Calculators

Pregnancy Calculator

The Pregnancy Calculator estimates your due date and current week of pregnancy based on the first day of your last menstrual period (LMP), using the standard 280-day gestation estimate.

How due dates are estimated

The most common method (Naegele's Rule) estimates a due date as 280 days (40 weeks) from the first day of your last menstrual period, assuming a typical 28-day cycle. If your cycle is longer or shorter than 28 days, this calculator adjusts the estimate accordingly.

Due Date = LMP + 280 days + (Cycle Length − 28)
Example: If your last period started on January 1st with a typical 28-day cycle, your estimated due date would be around October 8th, and ovulation/conception likely occurred around January 15th.

Trimesters

Pregnancy is typically divided into three trimesters: 1st (weeks 0–13), 2nd (weeks 13–27), and 3rd (weeks 27–40+). This is an estimate only — actual delivery dates vary. See our Due Date Calculator for other ways to estimate this, and the Conception Calculator to estimate conception date specifically.

Related Calculators

Due Date Calculator

Estimate your baby's due date from your last period or conception.

Pregnancy Conception Calculator

Estimate your likely conception date from your due date.