Calculate your due date, current pregnancy week, and track your baby's development
This is the first day of your last menstrual period (LMP). This is the standard method doctors use to calculate due dates.
If you know when you conceived (IVF, IUI, or confirmed ovulation date), enter it here for more accurate calculation.
If your doctor or ultrasound has already given you a due date, enter it here to see your current week and milestones.
0 of 40 weeks completed
This pregnancy calculator provides estimates based on standard 40-week pregnancies and should not replace professional medical care. Actual due dates can vary, and only 5% of babies are born exactly on their due date. Your healthcare provider may adjust your due date based on ultrasound measurements, which are more accurate than calculation methods. Always consult with your obstetrician or midwife for personalized pregnancy care, proper prenatal monitoring, and delivery planning. This tool is for informational purposes only.
This pregnancy calculator uses medically-accepted formulas to estimate your due date and current pregnancy week. Healthcare providers worldwide use these same calculation methods for initial pregnancy dating.
Pregnancy is dated from the first day of your last menstrual period, not from conception. This means you're technically "2 weeks pregnant" at conception. A full-term pregnancy is 40 weeks from LMP or 38 weeks from conception. Trimesters are divided as: First (weeks 1-12), Second (weeks 13-26), Third (weeks 27-40).
Use this pregnancy calculator when you need to:
Your due date is an estimate, not a deadline. About 70% of babies are born within 10 days (before or after) the due date. First-time mothers tend to deliver closer to 41 weeks, while subsequent pregnancies often deliver earlier. Full term is anywhere from 37-42 weeks. Don't panic if your due date passes - most providers won't induce until 41-42 weeks unless there are medical concerns. Keep this in mind when planning maternity leave or travel.
If your doctor performs a dating ultrasound in the first trimester (ideally 8-13 weeks), that measurement is more accurate than calculation from your last period. Early ultrasounds can date pregnancy to within 3-5 days accuracy because embryos grow at very predictable rates before 14 weeks. If there's a significant difference (more than 7 days) between your LMP date and ultrasound date, your provider will typically use the ultrasound date. Always defer to your healthcare provider's official due date.
Begin taking prenatal vitamins with at least 400mcg of folic acid 1-3 months BEFORE trying to conceive. Neural tube development (brain and spinal cord) happens in the first 28 days of pregnancy - often before you even know you're pregnant. Folic acid taken before conception reduces neural tube defects by 70%. If you're already pregnant and haven't been taking prenatals, start immediately and inform your provider. They may recommend higher folic acid doses (4mg) if you have risk factors.
Most providers schedule the first prenatal appointment around 8-10 weeks (counting from your last period). This timing allows for accurate dating ultrasound and hearing the heartbeat. If you have risk factors (previous miscarriage, chronic conditions, IVF pregnancy), your provider may want to see you earlier. Use this calculator to determine your current week and call your OB/GYN or midwife as soon as you have a positive pregnancy test to schedule that first appointment.
When someone says "I'm 12 weeks pregnant," they mean they've completed 12 weeks and are in their 13th week. This confuses many people. Additionally, you're "2 weeks pregnant" at conception because pregnancy is counted from your last period, not conception. A "40-week pregnancy" is actually 38 weeks from conception. When scheduling appointments, clarify whether your provider means "weeks completed" or "weeks + days" (like 12+3 meaning 12 weeks and 3 days). This calculator shows weeks completed plus remaining days.
First trimester (1-12 weeks): Dating ultrasound, initial bloodwork, genetic screening options (NIPT, NT scan). Second trimester (13-26 weeks): Anatomy scan (18-22 weeks), glucose screening (24-28 weeks), amniocentesis if indicated. Third trimester (27-40 weeks): Group B strep test (35-37 weeks), weekly monitoring if high-risk, discuss birth plan. Knowing your current trimester helps you prepare for upcoming tests and understand why certain screenings are offered. Don't skip recommended screenings - they catch issues early when interventions are most effective.
When planning maternity leave, assume you might deliver up to 2 weeks past your due date (common for first pregnancies). Many women plan leave starting on their due date, then feel stressed when they "go overdue" and have to work longer than expected. Consider starting leave 1-2 weeks before your due date, or have flexibility built in. Also remember that "6 weeks maternity leave" means 6 weeks from delivery, not from your due date. If you deliver at 41 weeks, you're already 1 week "over" and might feel rushed to return. Build buffer time into your planning.
This calculator provides estimates accurate to within 1-2 weeks for women with regular 28-day cycles. However, actual delivery dates vary significantly - only 5% of babies are born exactly on their calculated due date. If you have irregular cycles, the calculation will be less accurate. A first-trimester dating ultrasound (done between 8-13 weeks) is the most accurate dating method, with accuracy to within 3-5 days. Your healthcare provider may adjust your due date based on ultrasound measurements, and you should always use your provider's official due date for medical planning.
Medical convention dates pregnancy from the first day of your last menstrual period (LMP) because that date is known and consistent, while exact conception date is rarely known. Most women don't know exactly when conception occurred since sperm can survive up to 5 days and fertilization timing varies. Using LMP as the starting point has been standard medical practice for over a century and all prenatal care guidelines, screening schedules, and research are based on this dating method. This means you're technically "2 weeks pregnant" at conception.
This is a personal decision. Many women wait until after the first trimester (12 weeks) to announce publicly because miscarriage risk drops significantly after this point - from about 15% in the first trimester to 1-2% in the second trimester. However, some women prefer to tell close family and friends early so they have support if complications occur. Consider telling your employer earlier if you need accommodations for morning sickness or fatigue, or if your job involves hazards (heavy lifting, chemicals, radiation). There's no right or wrong answer - do what feels comfortable for your situation.
If you don't remember your last menstrual period date, your healthcare provider will perform a dating ultrasound to estimate how far along you are. Early ultrasounds (before 14 weeks) can accurately date pregnancy by measuring the embryo or fetus. If you're further along, ultrasound dating becomes less precise. Try to recall approximately when your last period was - even knowing "early December" or "around Thanksgiving" helps narrow the range. If you have irregular cycles or were on birth control, ultrasound dating is even more important.
Your due date can be adjusted based on first-trimester ultrasound measurements. If there's a significant difference (more than 7 days) between the date calculated from your last period and the ultrasound measurements, your provider will typically change your official due date to match the ultrasound. After the first trimester, due dates are rarely changed because later ultrasounds are less accurate for dating purposes - growth rates vary more between individual babies. Once you have an official due date from your provider, that date should remain consistent throughout your pregnancy.
Going past your due date is common, especially for first-time mothers. About 50% of first-time moms deliver after their due date. Most providers will allow pregnancy to continue until 41-42 weeks before discussing induction, as long as monitoring shows the baby is healthy. After 40 weeks, you'll likely have more frequent appointments (2-3 times per week) for non-stress tests and amniotic fluid checks. The decision to induce considers multiple factors: your age, medical history, baby's size, amniotic fluid levels, and your preferences. Post-dates induction reduces stillbirth risk, which increases slightly after 42 weeks.
First-time mothers typically feel movement (called "quickening") between 18-25 weeks, while women who've been pregnant before often feel it earlier, around 16-18 weeks. Early movements feel like flutters, bubbles, or gentle taps. By 24-28 weeks, movements become stronger and more frequent. After 28 weeks, your provider may ask you to do daily kick counts - you should feel at least 10 movements in 2 hours. Decreased movement after 28 weeks warrants immediate medical attention. Factors affecting when you feel movement include placental position (anterior placenta muffles sensation) and your body size.
The safest time to travel is during the second trimester (14-27 weeks) when morning sickness has usually subsided and you're not yet physically uncomfortable. Most airlines allow travel until 36 weeks for domestic flights and 32 weeks for international. After 28 weeks, bring a copy of your prenatal records in case you need medical care while traveling. Avoid traveling to areas with Zika virus, high altitude, or limited medical facilities. Stay hydrated, walk around every 1-2 hours to prevent blood clots, and wear seatbelts correctly (lap belt under bump, shoulder belt between breasts). Always check with your healthcare provider before booking travel.
Many people wait until after the 20-week anatomy scan to start buying baby items, especially if they want to know the sex. However, some essential items (car seat, crib) can take time to research and order, so starting earlier isn't wrong. Have your nursery set up and hospital bag packed by 36 weeks in case of early delivery. Essential items to have before delivery: car seat (required to leave hospital), bassinet or crib, diapers, wipes, basic clothing, and feeding supplies. You don't need everything immediately - babies outgrow items quickly. Consider borrowing big items or buying secondhand (except car seats, which should always be new).
This pregnancy calculator is based on obstetric standards and guidelines from these authoritative sources:
This pregnancy calculator was created to help expectant parents track their pregnancy journey and understand important milestones. All calculations are performed in your browser - your data is completely private and never stored or shared.
Created by: ToolsVault Health Tools Team
Based on: ACOG and WHO pregnancy guidelines
Last updated: January 25, 2026
Next review: May 2026