Due Date Calculator

If you don't know your LMP date, your healthcare provider can estimate it using early ultrasound. First trimester ultrasound (before 13 weeks) is accurate within ±3-5 days. Ultrasound dating becomes less accurate later in pregnancy. If you have irregular cycles, an early ultrasound is especially important for accurate dating. Contact your healthcare provider to schedule dating ultrasound if your LMP date is unknown.

Pregnancy is counted from your LMP date, not from conception. Most women discover pregnancy around 4-5 weeks (after a missed period). If your LMP was 4 weeks ago, you're considered 4 weeks pregnant, even though conception occurred about 2 weeks ago. This is why early pregnancy can seem confusing—the pregnancy age is always 2 weeks older than the baby's actual age. Your healthcare provider will confirm your exact gestational age with dating ultrasound.

If your menstrual cycle varies significantly (more than 7 days), standard due date calculation may be inaccurate. This calculator uses the standard 280 days (40 weeks) from LMP, which assumes a regular 28-day cycle. For irregular cycles, ultrasound dating is more reliable. You can adjust the cycle length in this calculator if your typical cycle is longer or shorter than 28 days. Always discuss your specific situation with your healthcare provider for accurate due date estimation.

Pregnancy typically lasts 37-42 weeks (full term). If you haven't delivered by your due date, it's not necessarily a problem—many pregnancies naturally extend beyond the due date. Your healthcare provider will monitor you closely with regular checkups, ultrasounds, and non-stress tests. If pregnancy extends significantly past 42 weeks, your provider may recommend labor induction to reduce risks. Never attempt to induce labor at home. Always follow your healthcare provider's guidance regarding post-due-date pregnancy management.

This calculator is designed for natural conception pregnancies. IVF pregnancies may have different dating because the exact conception date is known. For IVF pregnancies, your fertility clinic will provide a specific due date based on your embryo transfer date and stage (day 3 or day 5 transfer). Don't use this LMP-based calculator for IVF—use the due date provided by your fertility clinic. If you had IVF, discuss dating with your healthcare provider rather than using this calculator.

Pregnancy is typically 40 weeks (280 days) when counted from LMP. This is slightly longer than 9 calendar months (about 9.3 months). Medical professionals use weeks to date pregnancy because it's more precise than months. The 40-week count includes the approximately 2 weeks before actual conception (before you knew you were pregnant). Full term is considered 39-40 weeks. Babies born between 37-42 weeks are considered term. This is why pregnancy seems long—the count starts before conception!