Helpful Toolbox

Due Date Calculator

Enter the first day of your last period and see your estimated due date, how far along you are, and your current trimester.

📖 How it works & FAQ
—Estimated due dateLMP + 280 days
—How far alongweeks & days pregnant
—Trimestercurrent stage
—Time remaininguntil due date

This is an estimate only — always confirm your due date with your doctor or midwife.

How your due date is estimated

This calculator uses Naegele's rule, the standard method clinicians have used for over 200 years. It counts 280 days (40 weeks) forward from the first day of your last menstrual period (LMP). That single date drives everything: your estimated due date, how many weeks along you are today, and which trimester you're in. Only about 1 in 20 babies actually arrives on the exact due date — most healthy births happen anywhere from 37 to 42 weeks — so treat this as a helpful target, not a deadline.

Weeks and trimesters explained

Pregnancy is measured from your LMP, not from conception, which is why you're counted as roughly two weeks "pregnant" before the baby was even conceived. The three trimesters here follow the common split: the first trimester is weeks 1–13, the second is weeks 14–27, and the third is week 28 until birth. Knowing your current week helps you follow milestone guides, schedule prenatal appointments, and understand what your body and baby are doing.

How to use it

  1. Find the first day of your last menstrual period on a calendar.
  2. Enter that date in the field above — results update instantly.
  3. Read your estimated due date, how far along you are, your trimester, and the time remaining.
  4. Write the due date down and confirm it with your doctor or midwife at your next visit.

These results are estimates for general information only, not medical advice — always confirm with a qualified healthcare provider.

FAQ

What if I don't know my exact LMP date?
Use your best estimate, then ask about a dating ultrasound. Early ultrasounds (before 13 weeks) are the most accurate way to confirm or adjust a due date.
My cycle isn't 28 days — does that matter?
Naegele's rule assumes a 28-day cycle with ovulation around day 14. If your cycles run longer or shorter, your true due date may shift by a few days; your provider can fine-tune it.
Can this calculator diagnose anything?
No. It only does date math from the LMP you enter. It cannot confirm pregnancy, viability, or health — those require a clinical exam.
Is my information saved?
No. Everything runs privately in your browser. Nothing you type is uploaded, stored, or shared.