Pregnancy Calculator
Estimate your due date based on the first day of your last menstrual period (LMP).
Pregnancy Calculator – Estimate Your Due Date Easily
Our Pregnancy Calculator helps you estimate your due date and current gestational age based on the first day of your last menstrual period (LMP). This simple, free online tool provides an accurate estimate according to the standard 40-week pregnancy model used by doctors and midwives around the world.
How Does a Pregnancy Calculator Work?
The calculator works by adding 280 days (or 40 weeks) to the first day of your last period. This is based on the average menstrual cycle length of 28 days and assumes ovulation occurs on day 14. If your cycle is longer or shorter, the actual due date may differ slightly.
For example, if the first day of your last period was January 1, 2025, your estimated due date would be October 8, 2025. However, only about 5% of women give birth exactly on their due date — most deliver between 37 and 42 weeks of pregnancy.
Understanding Pregnancy Weeks
Pregnancy is typically divided into three main trimesters:
- First Trimester (Weeks 1–12): The body begins rapid hormonal changes. This is the most sensitive period for fetal development.
- Second Trimester (Weeks 13–27): Often called the “golden period,” many women experience less nausea and more energy.
- Third Trimester (Weeks 28–40): The baby gains weight, and you’ll prepare for delivery and labor.
Why Use a Pregnancy Calculator?
A pregnancy calculator helps you plan ahead — from scheduling medical appointments to monitoring fetal development and preparing for your baby’s arrival. Knowing your approximate due date allows healthcare providers to estimate important milestones, such as ultrasounds, genetic screenings, and glucose tests.
It’s also helpful for tracking your gestational age week by week, giving you insights into what’s happening in your body and your baby’s growth.
Important Notes
The estimated due date is just a guideline. Only a qualified healthcare provider can confirm your actual gestational age and expected delivery date through medical examination and ultrasound measurements. Remember that every pregnancy is unique, and small variations are completely normal.
Pregnancy Milestones by Trimester
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1–12 | Fertilization, heartbeat, and major organ formation begin. |
| Second | 13–27 | Baby starts to move; mother feels kicks; ultrasound imaging clearer. |
| Third | 28–40 | Rapid weight gain, final development, and preparation for birth. |
Useful Resources
Learn more about pregnancy and prenatal care from trusted sources:
Disclaimer: This Pregnancy Calculator provides general information for educational purposes and is not a substitute for medical advice. Always consult a qualified healthcare provider for personalized recommendations.