Five ways to estimate your due date — by last menstrual period, average cycle length, ovulation date, conception date, IVF transfer, or your current pregnancy week. See your due date, current week, trimester, and conception window instantly.
Standard is 28 days.
If entered, due date is calculated from your embryo transfer.
Most IVF transfers are day 5 blastocysts.
Already know how far along you are? Enter your current week — we'll work backwards to your due date. Used only when LMP, ovulation, conception and IVF are blank.
Your due date is calculated using Naegele's rule, the standard method used by obstetricians worldwide. It starts with the first day of your last menstrual period (LMP), adds 280 days (40 weeks), and then adjusts for your actual cycle length. For a 28-day cycle, the calculation is straightforward: LMP + 280 days. If your cycle is 30 days, 2 extra days are added; if it's 25 days, 3 days are subtracted. This adjustment accounts for when ovulation actually occurred in your cycle.
Standard due date calculations assume ovulation happens on day 14 of a 28-day cycle. But if your cycle is longer, ovulation occurs later — meaning conception happened later, and your true due date is a few days after the standard estimate. Conversely, a shorter cycle means earlier ovulation and an earlier due date. This is why entering your actual average cycle length improves accuracy. For example, with a 32-day cycle, ovulation likely happened around day 18, so your due date is 4 days later than the standard LMP + 280 calculation.
The most common method. Take the first day of your last menstrual period and add 280 days (40 weeks). This is Naegele's rule and assumes a 28-day cycle with ovulation on day 14. The calculator above adds or subtracts days automatically when your cycle is longer or shorter. Best for women with regular cycles who remember their last period date.
Formula: Due date = LMP + 280 days ± (cycle length − 28)
If you know your conception date — for example through fertility tracking or a single timed intercourse — your due date is exactly 266 days (38 weeks) after that day. Enter the conception date in the calculator and it will work backward to display your pregnancy week and due date.
Formula: Due date = Conception date + 266 days
If you tracked ovulation with LH (ovulation) test strips, basal body temperature, or cervical mucus, this method is more accurate than LMP — especially if your cycle is irregular. Conception happens within 24 hours of ovulation, so due date is the ovulation date plus 266 days.
Formula: Due date = Ovulation date + 266 days
IVF gives the most precise due date because the exact age of the embryo is known. For a day-5 blastocyst transfer, due date = transfer date + 261 days. For a day-3 embryo transfer, due date = transfer date + 263 days. The calculator handles both — just toggle Day 3 / Day 5 above and enter your transfer date.
Formula: Due date = Transfer date + (266 − embryo age) days
An estimated due date (EDD) is the calendar day on which a pregnancy is expected to complete 40 weeks of gestation from the first day of the last menstrual period. It's an estimate — not a deadline. A pregnancy is considered full term any time between 37 and 42 weeks, and your provider may adjust your EDD if a first-trimester ultrasound shows the embryo measuring more than 5–7 days off from the period-based estimate.
Due date calculators are a reliable starting point but are not exact. Only about 5% of babies are born on their estimated due date. Most arrive within two weeks before or after. Accuracy depends on the method used:
First Trimester
Weeks 1–12
Baby's major organs form. You may feel nausea, fatigue, and breast tenderness.
Second Trimester
Weeks 13–27
Energy often returns. Baby grows rapidly. Anatomy scan happens around week 20.
Third Trimester
Weeks 28–40+
Baby gains weight and prepares for birth. You may feel more discomfort and Braxton Hicks.
Conception occurs when sperm fertilizes the egg, which typically happens within 24 hours of ovulation. However, because sperm can survive in the female reproductive tract for up to 5 days, the "conception window" spans roughly 5 days before ovulation through 1 day after. If you know your ovulation date, conception likely happened on that day or within 24 hours. If you only know your cycle length, this calculator estimates ovulation and shows you that conception window. Keep in mind that exact conception timing is rarely known unless you were tracking ovulation precisely.
Week 4–5: Positive home pregnancy test possible
hCG levels rise enough to detect.
Week 6–8: First prenatal visit and heartbeat on ultrasound
Transvaginal ultrasound often used early.
Week 12: End of first trimester
Miscarriage risk drops significantly. Nuchal translucency scan may be offered.
Week 18–22: Anatomy scan (detailed ultrasound)
baby's organs, gender (if desired), and growth are checked.
Week 24: Viability milestone
Most babies born from this point can survive with intensive care.
Week 28: Third trimester begins
Glucose screening test for gestational diabetes.
Week 37: Full term
Baby is considered fully developed. Delivery can happen safely any time now.
Week 40: Estimated due date
Only about 5% of babies arrive exactly on their due date.
If your cycles vary by more than 7–9 days from month to month, a period-based due date estimate is less reliable. In this case, a first-trimester ultrasound is the gold standard for dating a pregnancy. Early ultrasound measures the embryo's crown-rump length, which is highly accurate for determining gestational age between 6 and 13 weeks. You can still use this calculator with your best estimate, but make sure to tell your provider that your cycles are irregular so they can schedule a dating ultrasound.
Your estimated due date is 40 weeks (280 days) from the first day of your last menstrual period, adjusted if your cycle is shorter or longer than 28 days. If you know your ovulation or conception date, the due date is 266 days from then.
This is known as Naegele's rule. The default assumes ovulation around day 14 of a 28-day cycle. If your cycle is longer or shorter, ovulation — and therefore your due date — shifts by the same number of days.
If you know your exact ovulation or conception date, the calculator uses that instead for a more accurate estimate (ovulation + 266 days).
Calculate your due date from your last menstrual period.
Find your average cycle length and predict your next period.
Estimate your due date based on your ovulation date.
Calculate your due date from a known conception date.
Find out exactly how many weeks pregnant you are today.
Track baby's growth week by week with milestones and tips.
See which trimester you're in and what to expect next.
Medicaid coverage and paid family leave status where you live.
This page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider for prenatal care and personalized pregnancy guidance.
Free printable planners and calculators built for women's wellness — no account needed.
Printable pregnancy week log, symptom tracker, appointment checklist and monthly review — the perfect companion to your due date.
All the tools and guides in this cluster, in one place.
Estimate your pregnancy due date.
Current pageCalculate due date from your last period.
OpenCalculate due date from conception date.
OpenCalculate due date from ovulation.
OpenFind out exactly how many weeks pregnant you are.
OpenTrack baby's growth week by week.
OpenSee which trimester you're in.
OpenCommon pregnancy symptoms by week and what they mean.
OpenHow to read early, common, and urgent pregnancy symptoms.
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