Pregnancy Calculator
Your Pregnancy Information
How It Works
Calculate your due date in three simple steps.
Step 1: Enter LMP Date
Provide the first day of your last menstrual period (LMP). This is the starting point for all pregnancy calculations.
Step 2: Enter Cycle Length
Enter your average menstrual cycle length. The standard is 28 days, but normal ranges from 20 to 45 days.
Step 3: Get Results
Click calculate to see your due date, current week, days remaining, trimester, and conception date. Copy any value with one click.
Understanding Pregnancy Calculation
Learn the key concepts behind due date estimation.
Gestational Age
Gestational age is counted from the first day of the LMP, not from conception. A full-term pregnancy reaches 280 days (40 weeks) of gestational age at birth.
Naegele's Rule
Naegele's Rule estimates the due date by adding 280 days (or 9 months + 7 days) to the LMP. It assumes a standard 28-day cycle with ovulation on day 14.
Cycle Length Adjustment
For cycles longer or shorter than 28 days, the due date shifts. Each extra day beyond 28 adds one day to the due date. Each day shorter subtracts one day.
First Trimester
Weeks 1 through 13. This is the most critical period for fetal organ development. Morning sickness, fatigue, and hormonal changes are most common during this phase.
Second Trimester
Weeks 14 through 26. Often called the "honeymoon phase" of pregnancy. Energy levels improve, the belly becomes visible, and fetal movements can be felt.
Third Trimester
Weeks 27 through 40. The baby grows rapidly and the mother may experience increased discomfort, swelling, and Braxton Hicks contractions as the body prepares for labor.
Conception Timeline
Conception typically occurs about 14 days after the LMP start. This means at the "moment of conception," you are already considered 2 weeks pregnant in gestational age terms.
Due Date Accuracy
Only about 4-5% of babies are born on their exact due date. Most arrive within a 2-week window around the estimated date. Due dates are estimates, not deadlines.
Ultrasound Dating
First-trimester ultrasound is the most accurate method for dating a pregnancy. It can confirm or adjust the LMP-based due date by measuring the fetus's size.
LMP Uncertainty
If the LMP date is uncertain due to irregular periods, bleeding irregularities, or recent birth control use, ultrasound dating becomes the primary method for estimating due date.
Multiple Pregnancies
Twins and higher-order multiples often deliver earlier than singletons. The average twin pregnancy lasts about 36-37 weeks instead of the standard 40 weeks.
Premature Birth
Birth before 37 weeks is considered premature. Babies born between 34-37 weeks are late preterm, and those born before 34 weeks may require specialized neonatal care.
Post-Term Pregnancy
Pregnancy extending beyond 42 weeks is considered post-term. Healthcare providers may recommend induction of labor to reduce risks to the baby in post-term pregnancies.
Quickening
Quickening refers to the first fetal movements felt by the mother, typically between weeks 16 and 25. It is an important milestone in pregnancy progression.
Fundal Height
Fundal height is the distance from the pubic bone to the top of the uterus. Measured in centimeters, it roughly corresponds to the number of weeks of pregnancy after 20 weeks.
Medical Disclaimer
This calculator provides estimates for informational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult your OB-GYN for personalized pregnancy care.
Limitations
LMP-based calculations assume regular ovulation timing. Variations in cycle length, ovulation day, and implantation timing mean actual delivery dates can differ significantly from estimates.
Key Features
Everything you need to track your pregnancy timeline.
Accurate Due Date
Estimates your due date using Naegele's Rule adjusted for your specific cycle length for a personalized calculation.
Current Week & Day
Shows exactly which week and day of pregnancy you are in, calculated from your LMP to the current date.
Trimester Detection
Automatically identifies whether you are in the 1st, 2nd, or 3rd trimester based on your current gestational week.
Days Remaining Counter
Displays the number of days left until your estimated due date, updated based on the current date.
Conception Date Estimate
Also calculates the estimated conception date by adding 14 days to your LMP for a complete pregnancy timeline.
Click-to-Copy Results
Click any result swatch or use the action buttons to copy the due date, current week, trimester, or all results instantly.
Custom Cycle Support
Accepts cycle lengths from 20 to 45 days, accounting for shorter and longer than average menstrual cycles.
100% Client-Side Privacy
All calculations happen locally in your browser. No pregnancy data, dates, or personal information are sent to any server.
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Frequently Asked Questions
Find answers to common questions about pregnancy calculations.
How is the due date calculated?
The due date is calculated using Naegele's Rule — adding 280 days to the LMP, then adjusting for your cycle length. For a 30-day cycle, 2 extra days are added. This accounts for ovulation occurring later in longer cycles.
Is the due date always accurate?
No. Only about 4-5% of babies are born on their exact due date. Most arrive within a two-week window around the estimated date. ACOG recommends first-trimester ultrasound for the most accurate dating.
What if I don't know my exact LMP date?
If you are unsure of your LMP, consult your healthcare provider. They can perform an ultrasound scan in the first trimester to estimate gestational age based on the baby's measurements.
What are the three trimesters?
The three trimesters are: First Trimester (weeks 1-13), Second Trimester (weeks 14-26), and Third Trimester (weeks 27-40). Each has distinct developmental milestones and different maternal symptoms.
How does cycle length affect the due date?
If your cycle is longer than 28 days, ovulation occurs later, pushing the due date forward. For example, a 35-day cycle adds 7 extra days. A 24-day cycle subtracts 4 days. This adjustment improves accuracy for non-standard cycles.
Can I use this calculator for IVF pregnancies?
For IVF pregnancies, LMP-based calculations may not be accurate. Your fertility clinic will provide a more precise due date based on the embryo transfer date or egg retrieval date.
What does "gestational age" mean?
Gestational age is the time elapsed since the first day of the LMP. It is about 2 weeks more than the fetal age (time since conception). Doctors use gestational age as the standard measurement.
Is my pregnancy data stored anywhere?
No. All calculations happen entirely in your browser using client-side JavaScript. No dates, cycle information, or personal data are sent to any server or stored in any way.