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Gestation Calculator Wheel

Free online pregnancy wheel calculator. Calculate your due date, gestational age, and track important pregnancy milestones. Works like an OB wheel without the spinning!

💡

Pregnancy is calculated as 40 weeks (280 days) from your last menstrual period

This is gestational age – fetal age is about 2 weeks less since conception occurs around day 14

✓Due Date Calculator
✓Gestational Age
✓Milestone Tracker

📅 Last Menstrual Period

21 days28 (average)35 days

💡 Tip: If you're unsure of your cycle length, use 28 days (the average). Your doctor may adjust the due date after your first ultrasound.

📊 Your Pregnancy Dates

Current Gestational Age

10w 0d

1st Trimester

🎯 Expected Due Date

Tue, Aug 18, 2026

210 days to go

Progress25%
Week 0Week 12Week 28Week 40

📋 Key Dates

Last Period (LMP)Nov 11, 2025
Est. ConceptionNov 25, 2025
2nd Trimester StartsFeb 10, 2026
3rd Trimester StartsMay 26, 2026

🗓️ Pregnancy Milestones

MilestoneWeekDateDescription
✅ Implantation3-4Dec 4, 2025Embryo implants in uterus
✅ First Heartbeat6Dec 23, 2025Heart begins to beat
✅ First Ultrasound8Jan 6, 2026Dating scan recommended
⏳ End of 1st Trimester12Feb 3, 2026Risk of miscarriage drops
👉 NT Scan / NIPT11-14Jan 27, 2026Genetic screening window
⏳ Anatomy Scan18-22Mar 31, 2026Detailed ultrasound
⏳ Viability24Apr 28, 2026Baby could survive if born
⏳ Glucose Test24-28May 12, 2026Gestational diabetes screening
⏳ 3rd Trimester Starts28May 26, 2026Final stage of pregnancy
⏳ Full Term37Jul 28, 2026Safe to deliver
⏳ Due Date40Aug 18, 2026Expected date of delivery

🤰 Understanding Pregnancy Dating

A gestation calculator wheel (also called a pregnancy wheel or OB wheel) is a tool healthcare providers have used for decades to estimate due dates and track pregnancy progress. Our digital version provides the same calculations without the need for a physical wheel.

How Due Dates Are Calculated

The standard method calculates pregnancy as 280 days (40 weeks) from the first day of your last menstrual period (LMP). This is called "Naegele's Rule." Since most women don't know their exact conception date, using LMP provides a consistent starting point.

📊 The Three Trimesters

1st Trimester (Weeks 1-12): Embryo develops, organs form, highest risk of miscarriage
2nd Trimester (Weeks 13-27): Baby grows rapidly, movement felt, anatomy scan done
3rd Trimester (Weeks 28-40): Baby gains weight, prepares for birth, you may feel tired

When Is Ultrasound Dating Used?

First-trimester ultrasound (between 8-12 weeks) is the most accurate method for dating pregnancy, typically within 3-5 days. Your healthcare provider may adjust your due date if the ultrasound differs significantly from your LMP-based calculation (usually by more than 5-7 days).

Why Due Dates Are Estimates

Only about 5% of babies are born on their exact due date. Most healthy babies arrive between 37-42 weeks. Your due date is best viewed as the middle of a window when baby might arrive, not a precise prediction.

📋 Quick Facts

• Full term: 40 weeks (280 days)

• Conception: ~Day 14 of cycle

• Viable: 24+ weeks

• Early term: 37-38 weeks

• Full term: 39-40 weeks

• Late term: 41 weeks

• Post term: 42+ weeks

🚨 When to Call Your Doctor

• Heavy bleeding or spotting

• Severe abdominal pain

• Fever over 100.4°F (38°C)

• Decreased fetal movement

• Signs of labor before 37 weeks

Frequently Asked Questions

A pregnancy wheel (also called gestation calculator or OB wheel) calculates your due date by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). It assumes a standard 28-day cycle with ovulation occurring on day 14. If your cycle is longer or shorter, the calculator adjusts accordingly. For example, with a 35-day cycle, ovulation likely occurs around day 21, so 7 days are added to the standard calculation.

A gestational age calculator based on LMP is most accurate when you have regular menstrual cycles and know the exact date of your last period. It's typically accurate within 1-2 weeks. However, first-trimester ultrasound (between 8-12 weeks) is considered the gold standard for dating pregnancy, with accuracy within 3-5 days. Your healthcare provider may adjust your due date based on ultrasound measurements.

Gestational age is calculated from the first day of your last menstrual period (LMP), while fetal age (also called conceptional age) is calculated from the actual date of conception. Since conception typically occurs about 2 weeks after LMP, fetal age is always about 2 weeks less than gestational age. Healthcare providers use gestational age as the standard measurement for pregnancy.

The first trimester spans weeks 1-12, covering initial development and organ formation. The second trimester is weeks 13-27, when the baby grows rapidly and you may feel movement. The third trimester is weeks 28-40, preparing for birth. However, some sources define trimesters slightly differently (e.g., second trimester starting at week 14), so always confirm with your healthcare provider.

If you have irregular cycles, LMP-based calculations may be less accurate. In this case, early ultrasound dating becomes more important. You can still use this calculator with your best estimate of LMP, but discuss the results with your healthcare provider. They may adjust your due date based on ultrasound measurements, especially if there's a significant discrepancy.

Yes! If you know your conception date (for example, from IVF or tracked ovulation), you can calculate your due date by adding 266 days (38 weeks). Our calculator's ultrasound tab allows you to enter a known gestational age from a specific date, which works similarly. Conception-based dating is often more accurate than LMP-based calculation.

⚠️ Medical Disclaimer: This calculator provides estimates for informational purposes only and is not a substitute for professional medical advice. Pregnancy dating can vary based on individual circumstances. Always consult with your healthcare provider for accurate pregnancy dating and prenatal care. If you have concerns about your pregnancy, contact your doctor or midwife immediately.