Pregnancy Calculator
Track your due date instantly 🤰 100% free, fast, and trusted 🔒 Check your pregnancy timeline now ✨
PREGNANCY DETAILS
Estimated Due Date
Current Pregnancy Age
Trimester
Track your due date instantly 🤰 100% free, fast, and trusted 🔒 Check your pregnancy timeline now ✨
A Pregnancy Calculator is a simple tool that estimates important pregnancy milestones based on specific medical inputs such as the first day of your last menstrual period (LMP), conception date, due date, or ultrasound data. It helps determine your estimated due date (EDD), current gestational age in weeks and days, trimester stage, and key development periods. This tool follows standard obstetric calculation methods used by healthcare professionals to provide a reliable pregnancy timeline.
Pregnancy is typically measured as 40 weeks (280 days) from the first day of the last menstrual period, not from the conception date. Because ovulation usually occurs about 14 days after the start of a regular 28-day cycle, medical professionals calculate pregnancy age slightly differently than many people expect. A pregnancy calculator simplifies this process by automatically computing gestational weeks, remaining days until delivery, and trimester progress without manual date counting.
For example, if your last menstrual period started on January 1, the estimated due date would be calculated by adding 280 days. The calculator performs this instantly and also shows how many weeks pregnant you are today. This is especially helpful for tracking prenatal appointments, monitoring fetal growth stages, and planning maternity leave or delivery arrangements.
The Pregnancy Calculator works by applying standard obstetric formulas to the date you provide. The most common method is Naegele’s Rule, which estimates the due date using the formula: Estimated Due Date = LMP + 1 year − 3 months + 7 days. In simplified form, it is often calculated as LMP + 280 days. This method assumes a regular 28-day menstrual cycle.
Step 1: Enter the first day of your last menstrual period. Step 2: The calculator adds 280 days to determine the estimated due date. Step 3: It calculates the difference between today’s date and your LMP to determine your current gestational age in weeks and days. Step 4: It divides the pregnancy into trimesters: First trimester (week 1–13), second trimester (week 14–27), and third trimester (week 28–40).
If you know your conception date instead of LMP, the calculation adjusts slightly. In that case, the estimated due date is typically Conception Date + 266 days, because conception generally occurs about 14 days after LMP in a regular cycle. The calculator automatically handles these variations, including leap years and different month lengths, ensuring accurate date differences without manual errors.
A Pregnancy Calculator is useful from the earliest stage of pregnancy confirmation. Once you receive a positive pregnancy test, you can enter your last menstrual period to estimate how many weeks pregnant you are. This helps you schedule your first prenatal visit, which usually occurs between weeks 8 and 10.
It is also helpful for tracking trimester changes and understanding fetal development stages. For example, if the calculator shows you are 20 weeks pregnant, you are in the middle of the second trimester, when anatomy scans are typically performed. Knowing your gestational age allows you to prepare for medical screenings such as glucose tolerance testing around 24–28 weeks.
Expecting parents also use the calculator for planning purposes. It helps estimate maternity leave timing, baby shower scheduling, hospital registration, and financial preparation. If your cycle is irregular or you conceived through assisted reproductive methods, the calculator can still provide a structured estimate, though ultrasound dating may refine accuracy.
The core logic of a Pregnancy Calculator is based on date-difference computation and standardized gestational formulas. The system first converts input dates into a consistent date format. Then it calculates total days between the LMP and the current date using: Gestational Age (days) = Current Date − LMP. The total days are divided by 7 to determine completed weeks, and the remainder gives additional days.
To determine the estimated due date, the calculator adds 280 days to the LMP or 266 days to the conception date. The formula can be expressed as: EDD = Input Date + Standard Gestation Days. The program accounts for leap years and varying month lengths to maintain calendar accuracy. This prevents miscalculations that may occur when counting months manually.
The calculator may also compute pregnancy progress percentage using: Pregnancy Progress (%) = (Gestational Days ÷ 280) × 100. For example, if you are 140 days pregnant, you are approximately 50 percent through the pregnancy. These structured calculations provide a clear timeline and ensure consistent, medically aligned estimates.
Is the Pregnancy Calculator accurate?
The calculator provides medically standard estimates based on obstetric formulas. However, only a healthcare provider and ultrasound examination can confirm the most accurate due date.
Why is pregnancy counted from the last menstrual period?
Because the exact date of conception is often unknown, medical professionals use the first day of the last menstrual period as a consistent starting reference.
What if I have irregular periods?
If your cycle length varies significantly, the estimate may differ slightly. An early ultrasound scan can help refine gestational dating.
Can I calculate weeks and trimesters automatically?
Yes. The calculator instantly converts total gestational days into weeks, days, and trimester stages without manual counting.
Does this replace medical advice?
No. This tool is for estimation and planning purposes. Always consult a qualified healthcare professional for medical guidance and prenatal care decisions.