OptiDrop

Pregnancy Due Date Calculator Online — Estimate Your Due Date

Calculate your estimated due date based on your last menstrual period (LMP). See your current week of pregnancy, trimester, days remaining, and upcoming milestones. No upload, no sign-up — runs entirely in your browser.

Standard is 28 days. Adjust if your cycle is different.

Free Pregnancy Due Date Calculator

OptiDrop's Pregnancy Due Date Calculator estimates your baby's arrival date using Naegele's rule, the standard medical method for calculating due dates. Simply enter the first day of your last menstrual period (LMP) and your average cycle length. The calculator adds 280 days (40 weeks) to your LMP, adjusting for cycle lengths that differ from the standard 28 days.

Track Your Pregnancy Progress

Beyond the due date, this calculator shows your current gestational week, which trimester you are in, how many days have elapsed, and how many days remain. The milestone list highlights key developmental events for the next 4 weeks, helping you understand what to expect during each stage of your pregnancy.

Important Disclaimer

This calculator provides an estimate based on standard medical formulas. Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the estimated date. Always consult your healthcare provider for personalized prenatal care and accurate dating through ultrasound examinations.

Frequently Asked Questions

The due date is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle. If your cycle is longer or shorter, the calculator adjusts accordingly by adding or subtracting the difference from 28 days. Only about 5% of babies are born on their exact due date.
Gestational age is the age of the pregnancy measured from the first day of the last menstrual period (LMP). It is typically expressed in weeks. For example, if your LMP was 12 weeks ago, you are 12 weeks pregnant. Gestational age is about 2 weeks longer than fetal age (the actual age of the baby), because it includes the time before conception.
Due date calculations are estimates. Only about 5% of babies are born on their exact due date. Most babies are born within 2 weeks before or after the estimated due date. The accuracy depends on how well you remember your last menstrual period and whether your cycles are regular. Ultrasound dating in the first trimester provides the most accurate estimate.
A trimester is one of the three phases of pregnancy, each lasting approximately 13 weeks. The first trimester (weeks 1-13) involves major organ development. The second trimester (weeks 14-27) is often called the 'comfortable' period when many early symptoms ease. The third trimester (weeks 28-40) involves rapid growth and preparation for birth.

Last updated: June 2026