I'm Pregnant — When Is My Baby Actually Due? (Free 2026 Week-by-Week Calculator)

The tool uses Naegele's Rule — the same 280-day formula obstetricians have used for over a century. Pick one of two modes:

Last Menstrual Period (LMP): First day of your last period + 280 days = estimated due date. Best if you have regular ~28-day cycles.

Conception date: Conception date + 266 days = estimated due date. Best if you tracked ovulation, used OPKs, or conceived through IVF.

Enter one date, tap calculate, and you instantly see your EDD, current gestational week and day, trimester, and a countdown to delivery. Everything runs in your browser — your health data never leaves your device.

Your due date is the anchor for your entire prenatal care schedule. Every ultrasound, blood test and screening — from the dating scan at 8–12 weeks to the anatomy scan at 20 weeks to the glucose test at 24–28 weeks — is timed against it.

It also signals when your baby is safe to arrive. A birth at 37 weeks is early term; 39–40 weeks is full term; 42+ weeks is post-term and usually triggers medical induction.

For deeper background, the American College of Obstetricians and Gynecologists (ACOG) and the UK NHS pregnancy hub publish the reference timelines our calculator matches.

Use the LMP method if: your periods are regular (26–30 days), you remember the first day of your last period, and you don't know your exact conception date. This is the default doctors use.

Use the conception date method if: you tracked ovulation with basal body temperature or OPKs, you conceived via IVF (use your transfer date adjusted for embryo age), or your cycles are irregular.

Not sure? Try both in our Pregnancy Due Date Calculator and compare. A first-trimester ultrasound will confirm the final date within 3–5 days.

Weeks 1–4: Fertilization, implantation, hCG rises (this is what home tests detect). You may not feel anything yet.

Weeks 5–8: The heart starts beating around week 6. Brain, spinal cord and limb buds form. Morning sickness typically peaks. Baby is raspberry-sized by week 8.

Weeks 9–12: The embryo officially becomes a fetus. Fingers, toes and facial features appear. By week 12 baby is lime-sized and the miscarriage risk drops sharply.

Key first-trimester tests: confirmation blood work, dating ultrasound (8–12 weeks), nuchal translucency screening (11–13 weeks), optional NIPT.

Most nausea eases, energy returns, and around week 18–20 you feel the first flutters — the quickening. The anatomy scan at 20 weeks is the big milestone: detailed imaging of every organ, and (if you want) baby's sex.

By week 24 your baby reaches the medical viability threshold. By week 27 they can open their eyes, hear your voice, and weigh about 2 pounds.

Watch for: Braxton Hicks (practice contractions), back pain, mild swelling, stronger appetite. The glucose screening test happens between weeks 24–28.

This is the growth sprint. Baby gains about half a pound per week, lungs mature, and the brain wires rapidly.

Week 28–32: Fat layers build, movements become stronger. Start daily kick counts.

Week 33–36: Baby drops into the pelvis. Lungs are nearly ready. GBS test at 35–37 weeks.

Week 37–40: Baby is full term at 39 weeks. Only ~4% of babies actually arrive on the exact due date — most come within two weeks either side.

Time to pack the hospital bag, finalize the birth plan and pick a pediatrician. Use our calculator's countdown to keep the checklist on schedule.

Week 4: Positive pregnancy test • Week 6: Heartbeat detectable on ultrasound • Week 8: All major organs forming • Week 12: End of first trimester, miscarriage risk drops.

Week 16: Facial expressions • Week 20: Halfway point + anatomy scan • Week 24: Viability milestone • Week 27: Eyes open.

Week 28: Third trimester begins • Week 32: Practice breathing movements • Week 36: Nearly full size • Week 37: Early term • Week 39: Full term • Week 40: Due date 🎉.

The formula is medically standard, but biology varies. Only 4–5% of babies are born on their exact due date; the rest arrive anywhere in a two-week window. First-time mothers tend to deliver slightly later; second-time moms often earlier.

The most accurate confirmation is a first-trimester dating ultrasound — accurate to within 3–5 days. Our calculator gives you the same starting number your doctor uses.

Nutrition: Prenatal vitamin with 400–800 mcg folic acid, iron-rich foods, 1,000 mg calcium/day, omega-3s (avoid high-mercury fish), 8–10 glasses of water. Track daily water intake with our free Water Intake Calculator.

Movement: 150 minutes/week of moderate activity — walking, swimming, prenatal yoga. Skip contact sports.

Sleep & mental health: 7–9 hours, side-sleeping from the second trimester, and honest conversations with your partner or therapist.

Avoid: smoking, alcohol, unpasteurized foods, raw meat, changing cat litter.

Book your first prenatal appointment at 6–8 weeks. Between visits, contact your provider right away if you experience heavy vaginal bleeding, severe abdominal pain, fever above 100.4°F (38°C), sudden facial or hand swelling, severe headaches with vision changes, leaking fluid, decreased fetal movement after week 28, or any contractions before week 37.

✅ 100% free — no sign-up, no ads, no upsells.
✅ Both LMP and conception-date modes in one screen.
✅ Instant results — EDD, current week, trimester, countdown and milestones.
✅ Private by design — everything runs in your browser; nothing is uploaded.
✅ Mobile-first — works perfectly on your phone at 2 a.m.
✅ PDF export — download a branded report as fastdailytools.online_pregnancy-due-date-calculator.pdf to share with your partner or doctor.

Try it now → fastdailytools.online/pregnancy-due-date-calculator. Also useful during pregnancy: our Period Calculator, Diet Plan Calculator and Water Intake Calculator.