Pregnancy Calculator
Calculate your pregnancy progress, weeks pregnant, and due date.
Pregnancy Information
Please enter the first day of your last menstrual period
Pregnancy Progress
Enter your LMP to calculate pregnancy progress
About This Calculator
The Pregnancy Calculator helps you track your pregnancy progress, determine how many weeks and days you are pregnant, identify your current trimester, and calculate your estimated due date. This information is essential for understanding your pregnancy timeline and planning.
Pregnancy is calculated from the first day of your last menstrual period (LMP), which is typically about 2 weeks before conception. A full-term pregnancy is approximately 40 weeks (280 days) from LMP, or 38 weeks (266 days) from conception.
Formula & Calculation Method
Pregnancy Calculation:
Days Pregnant = Current Date - Last Menstrual Period
Weeks Pregnant = Days Pregnant ÷ 7
Days in Week = Days Pregnant % 7
Due Date = LMP + 280 days - (Cycle Length - 28)
Conception Date = LMP + (Cycle Length ÷ 2) - 1
Trimesters:
First: Weeks 0-12
Second: Weeks 13-26
Third: Weeks 27-40+
Pregnancy dating uses the first day of your last menstrual period as day 1, even though conception typically occurs about 2 weeks later. This standard method ensures consistent dating across all pregnancies and healthcare providers.
How to Use This Calculator
- Enter Last Period: Input the first day of your last menstrual period (LMP).
- Enter Cycle Length: Input your average menstrual cycle length in days.
- View Results: See weeks/days pregnant, current trimester, due date, and pregnancy milestones.
Frequently Asked Questions
How accurate is the due date?
Due dates calculated from LMP are accurate for about 80% of pregnancies. An early ultrasound (around 8-12 weeks) provides the most accurate due date. Only about 5% of babies are born exactly on their due date.
Why is pregnancy counted from LMP and not conception?
Pregnancy is counted from LMP because it's easier to identify the start of your last period than the exact day of conception. This adds about 2 weeks to the pregnancy timeline, making a full-term pregnancy 40 weeks from LMP (38 weeks from conception).
What if I don't know my last period date?
If you're unsure of your LMP, an early ultrasound can determine gestational age and provide a more accurate due date. Your healthcare provider can help calculate this based on fetal measurements.
Can the due date change?
Yes, your healthcare provider may adjust your due date based on early ultrasound measurements, especially if there's a significant difference from the LMP calculation. First-trimester ultrasounds are most accurate for dating.
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Calculator by
NumCalculators Editorial Team
Multi-disciplinary Expert Team