Pregnancy Calculator - Free Due Date Calculator
Calculate your pregnancy due date, gestational age, and track your pregnancy journey week by week. Get accurate estimates for conception date, trimesters, and important pregnancy milestones.
How Pregnancy Calculation Works
Step 1: Determine Starting Point
The calculation begins with either your Last Menstrual Period (LMP), conception date, or known due date from ultrasound.
Step 2: Apply Naegele's Rule
For LMP method: Add 280 days (40 weeks) to the first day of your last menstrual period.
Step 3: Adjust for Cycle Length
If your cycle is longer or shorter than 28 days, the due date is adjusted accordingly.
Step 4: Calculate Current Week
Determine your current pregnancy week by comparing today's date with your pregnancy start date.
About This Pregnancy Calculator
Our pregnancy calculator provides accurate estimates for due dates, gestational age, and pregnancy milestones based on well-established medical formulas. The calculator uses Naegele's Rule, which is the standard method used by healthcare providers worldwide.
Key Features:
- Multiple calculation methods (LMP, conception date, or due date)
- Adjustable cycle length for personalized accuracy
- Trimester information and current week calculation
- Important pregnancy milestones and dates
- Mobile-friendly and easy to use interface
How to Use the Pregnancy Calculator
- Select Calculation Method: Choose between Last Menstrual Period (LMP), Conception Date, or Known Due Date.
- Enter Date: Input the relevant date based on your selected method.
- Adjust Cycle Length: If you know your average cycle length differs from 28 days, adjust accordingly.
- Calculate: Click the calculate button to get your pregnancy information.
- Review Results: Check your due date, current week, trimester, and other important information.
- Share or Save: Use the share buttons to save or share your results.
Formula Used
Naegele's Rule Formula:
Due Date = LMP + 280 days + (Cycle Length - 28) days
Alternative Calculations:
- From Conception Date: Conception Date + 266 days
- From Due Date: Reverse calculation to determine LMP and current week
- Gestational Age: (Current Date - LMP) / 7 weeks
Note: These calculations provide estimates. Ultrasound dating, especially in the first trimester, is considered more accurate than LMP-based calculations.
Use Cases / Applications
For Expectant Mothers:
- Planning pregnancy journey
- Tracking pregnancy progress
- Preparing for prenatal appointments
- Planning maternity leave
- Organizing baby preparations
For Healthcare Providers:
- Initial due date estimation
- Scheduling prenatal care
- Patient education tool
- Quick reference calculation
- Pregnancy dating verification
Calculation Examples
Example 1: Standard 28-day Cycle
- LMP: January 1, 2024
- Cycle Length: 28 days
- Due Date: October 8, 2024
- Conception Date: Around January 15, 2024
Example 2: Longer Cycle
- LMP: January 1, 2024
- Cycle Length: 32 days
- Due Date: October 12, 2024 (4 days later)
- Conception Date: Around January 19, 2024
Example 3: From Conception Date
- Conception Date: January 15, 2024
- Due Date: October 8, 2024
- Estimated LMP: January 1, 2024
Frequently Asked Questions
How accurate is the pregnancy calculator?
The pregnancy calculator is highly accurate for estimating due dates based on the last menstrual period. However, only about 5% of babies are born exactly on their due date. Most babies are born within 2 weeks before or after the estimated due date. Ultrasound dating in early pregnancy (first trimester) is considered more precise than LMP-based calculations.
What if I don't remember my last menstrual period?
If you don't remember your LMP, you can use the conception date method if you know when conception occurred. Alternatively, consult with your healthcare provider for ultrasound dating, which can provide accurate gestational age estimates, especially in early pregnancy.
Should I adjust for irregular cycles?
Yes, if you have irregular cycles, the standard 28-day calculation may not be accurate. You can adjust the cycle length in our calculator, or better yet, use the conception date method if you know when conception occurred. For very irregular cycles, ultrasound dating is recommended.
When do the trimesters begin and end?
The three trimesters are: First trimester (weeks 1-12), Second trimester (weeks 13-26), and Third trimester (weeks 27-40). These are calculated from the first day of your last menstrual period.
Can I use this calculator for IVF pregnancies?
For IVF pregnancies, the conception date method would be more accurate since you know the exact date of embryo transfer. Add 266 days to the transfer date for a 5-day blastocyst transfer, or 268 days for a 3-day transfer.
Why is pregnancy calculated from the last menstrual period?
Pregnancy is calculated from the LMP because it's easier to determine than the exact conception date. Most women know when their last period started, but conception can occur anywhere from 11-21 days after the LMP, depending on cycle length and ovulation timing.