Can I calculate my due date from conception date instead of LMP?

Yes. If you know your conception date, add 266 days (38 weeks) to get your estimated due date. Our pregnancy calculator supports both LMP-based and conception-date-based calculations. Simply select the 'Conception Date' input option.

When is my baby's viability date (survival outside womb)?

Medical viability is generally considered to begin at 24 weeks of pregnancy. Babies born at 24–28 weeks have survival rates ranging from 39% to 80% with intensive neonatal care, according to leading neonatology guidelines. Our calculator shows your viability date automatically.

What week should I have my first prenatal appointment?

Most healthcare providers recommend your first prenatal visit at 8–10 weeks of pregnancy. However, if you have a high-risk pregnancy, irregular periods, or a history of miscarriage, you may be seen earlier. In the US and UK, a dating ultrasound is typically scheduled between 10–14 weeks.

How accurate is the pregnancy due date calculator?

Our calculator uses Naegele's Rule (LMP + 280 days), the same standard used by OBGYNs worldwide. It is accurate to the day given a reliable LMP date. However, only about 5% of babies are born exactly on their due date — most arrive within 2 weeks before or after. An ultrasound scan provides additional accuracy.

🤰 Free Tool — No Sign-Up Required

Pregnancy Calculator 2026 —
Due Date, Weeks & Baby Milestones

Enter your last menstrual period (LMP) or conception date to instantly get your due date, current pregnancy week, trimester, and a complete week-by-week baby development timeline.

✔ Naegele's Rule ✔ Trimester Tracker ✔ 40-Week Timeline ✔ Key Dates & Milestones ✔ Works Worldwide

📅 Page last updated: May 1, 2026 · Calculator updated daily

📅 Today —

📆 Day of Year —

🗓️ Week of Year —

🔢 Days Left in 2026 —

🤱 40-wk Due from Today —

Live · Based on today

🤰 Pregnancy Calculator

Choose your input method — use your Last Menstrual Period (LMP) for the most accurate result. If you know your conception date, use that option instead.

First Day of Last Menstrual Period (LMP) Enter the date your last period started. This is the standard method used by doctors globally.

Average Cycle Length (days) Most women have a 21–35 day cycle. Default is 28 days.

Ultrasound Date (optional) If you had an early dating ultrasound, enter its date here.

Estimated Due Date (EDD)

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Weeks Pregnant

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Trimester

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Days Until Birth

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LMP Date

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Last Period

Conception (Est.)

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±2–3 days

Viability Date

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Week 24

📊 Pregnancy Progress —

Week 1 Week 13 · T2 Week 27 · T3 Week 40

🗓️ Your Key Pregnancy Dates

📖 Week-by-Week Pregnancy Guide

Jump to week:

What Is a Pregnancy Calculator and How Does It Work?

A pregnancy calculator is a free digital tool that estimates your due date (EDD — Estimated Date of Delivery), how far along you are in your pregnancy, which trimester you're in, and upcoming milestones for both mother and baby. Our free online pregnancy calculator 2026 is used by expecting parents in the USA, UK, Canada, Australia, Germany, UAE, and across 150+ countries.

The Formula: Naegele's Rule (Standard Medical Method)

The globally accepted standard for due date calculation is Naegele's Rule, formulated by German obstetrician Franz Karl Naegele in the 19th century and still used in every hospital worldwide:

Estimated Due Date (EDD) = LMP + 280 days (40 weeks)

Equivalently: EDD = First day of LMP + 9 months + 7 days

Example: If your LMP was January 1, 2026:
EDD = January 1 + 280 days = October 8, 2026

For cycles longer or shorter than 28 days, the ovulation date shifts and so does the due date. Our calculator adjusts for custom cycle lengths (21–45 days) automatically, improving accuracy over the standard formula.

How to Use This Pregnancy Calculator

Using our free pregnancy week calculator is simple:

Step 1: Select your input method — LMP (Last Menstrual Period), Conception Date, or Known Due Date.
Step 2: Enter the date. For LMP, use the first day of your last period. For conception, use your best estimate (often 14 days after LMP for a 28-day cycle).
Step 3: Optionally enter your cycle length (default 28 days) for a more personalized result.
Step 4: Click "Calculate" to instantly see your due date, weeks pregnant, trimester, and full key dates timeline.

Understanding Trimesters: A Global Guide

Pregnancy is divided into three trimesters, each with distinct developmental milestones:

First Trimester (Weeks 1–13): The embryo forms all major organs. Morning sickness, fatigue, and breast tenderness are common. A dating ultrasound is typically done at 10–14 weeks in the US and UK.
Second Trimester (Weeks 14–27): Often called the "golden trimester" — energy returns, baby movements begin (~18–22 weeks), and the gender can often be determined. An anatomy scan (20-week scan) is standard in Australia, Canada, and the UK.
Third Trimester (Weeks 28–40+): Rapid weight gain, preparation for birth. In the USA, Group B Strep testing occurs at 35–37 weeks. The baby is considered full-term at 39–40 weeks per WHO guidelines.

Who Uses a Pregnancy Calculator?

Our free pregnancy calculator is designed for expecting mothers worldwide — whether you're in the US tracking your OBGYN visits, in the UK planning your NHS scans, in Australia preparing for your 20-week anatomy scan, in Canada tracking your Maternal-Fetal Medicine referrals, or anywhere else globally. It's also widely used by fertility specialists, midwives, and prenatal nurses for a quick gestational age reference.

❓ Frequently Asked Questions — Pregnancy Calculator 2026

How do I calculate my pregnancy due date from my last period? ▾

Add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is Naegele's Rule, the standard method used by OBGYNs, midwives, and hospitals worldwide. Our free pregnancy calculator does this automatically — just enter your LMP date and get your due date instantly, along with trimester, weeks pregnant, and baby milestones.

How many weeks pregnant am I right now? ▾

Enter the first day of your last menstrual period (LMP) into our pregnancy calculator above. It instantly shows how many weeks and days pregnant you are today, based on today's actual date. Pregnancy is counted from the first day of your LMP, not from conception — which means you are technically "2 weeks pregnant" on the day of conception in standard medical counting.

What are the 3 trimesters and when do they start and end? ▾

The First Trimester runs from Week 1 to Week 13 (approx. months 1–3). The Second Trimester runs from Week 14 to Week 27 (months 4–6). The Third Trimester runs from Week 28 to Week 40+ (months 7–9). Each trimester brings distinct changes in baby development and maternal symptoms. Our calculator shows which trimester you're currently in and how far through it you are.

What is the difference between gestational age and fetal age? ▾

Gestational age counts from the first day of your LMP, which is what doctors always use — it adds approximately 2 weeks before conception. Fetal age (or embryonic age) counts from actual conception and is about 2 weeks less than gestational age. For example, if you're 10 weeks pregnant (gestational), your baby is actually about 8 weeks old (fetal age). Our calculator uses the standard gestational age method.

Can I calculate my due date from my conception date? ▾

Yes! Select the "Conception Date" tab in our calculator above. Add 266 days (38 weeks) to your conception date to get your estimated due date. Conception typically occurs around 10–16 days after your LMP starts (ovulation day varies by cycle length). If you tracked ovulation with LH strips or a fertility monitor, you may know this date quite accurately.

When is my baby's viability date — when can a baby survive outside the womb? ▾

Medical viability begins at approximately 24 weeks of gestational age. At this point, survival with intensive neonatal care (NICU) becomes possible. Survival rates improve significantly from 24 (39%) to 28 weeks (85%) and beyond, according to leading neonatology data from the US, UK, and Australia. Our calculator shows your specific viability date (LMP + 168 days = Week 24). Always consult your OB/GYN for clinical guidance.

How accurate is this pregnancy due date calculator? ▾

Our calculator applies Naegele's Rule — the same standard used by every OB/GYN, midwife, and NHS/AHA guideline globally — and is accurate to the day given a reliable LMP. However, only about 5% of babies are born exactly on their EDD. Most arrive within 2 weeks before or after. A first-trimester ultrasound (7–12 weeks) provides the most accurate dating. Our tool adjusts for custom cycle lengths (21–45 days) beyond the default 28 days for greater accuracy.

What prenatal appointments should I have and when? ▾

Standard prenatal care (US/UK/Canada/Australia): First visit at 8–10 weeks (confirm pregnancy, blood tests, genetic screening discussion). Dating ultrasound at 10–14 weeks. Anatomy scan (20-week scan) at 18–22 weeks. Glucose tolerance test at 24–28 weeks. Group B Strep test at 35–37 weeks (US). Weekly/biweekly visits from 36 weeks onward. Our key dates timeline shows you which milestones are coming up based on your due date.

Pregnancy Calculator 2026 —Due Date, Weeks & Baby Milestones