Pregnancy Calculator

What Is a Pregnancy Calculator?

A Pregnancy Calculator is a free online tool that estimates your due date, pregnancy weeks, trimester, and upcoming milestones. It uses information such as your last menstrual period, conception date, ultrasound report, or IVF transfer date.

Our calculator works as a pregnancy week calculator and pregnancy date calculator, helping you estimate how many weeks pregnant you are and how much time remains until your due date.

It also provides a pregnancy tracker with progress information and a week-by-week schedule. You can use these estimates to understand your pregnancy timeline, but they do not replace medical advice or prenatal care.

How to Use the Pregnancy Calculator

Follow these steps to calculate your pregnancy timeline:

1. Select Calculate Based On: Choose Last period, Due date, Conception date, Ultrasound, or IVF transfer date.

2. Enter Your Information: Provide the date required for your selected method.

3. Complete Additional Fields: For Last period, select your average cycle length. For Ultrasound, enter gestational age in weeks and days. For IVF, select embryo age: day 3, day 5, or day 6.

4. Click Calculate: View your estimated due date, pregnancy week, trimester, and other results.

5. Review Pregnancy Progress: Check your weeks remaining, likely conception date, next milestone, and progress bar.

6. View the Week-by-Week Schedule: Explore the estimated pregnancy timeline.

7. Click Clear: Reset the calculator for another calculation.

If you are searching for a how many weeks pregnant calculator, select the dating method that matches the information you have and review the Current Week result.

How Is a Pregnancy Due Date Calculated?

Pregnancy is generally dated from the first day of the last menstrual period. A standard estimated due date is 280 days, or 40 weeks, from that date.

However, the exact calculation depends on your selected method.

1. Last Menstrual Period (LMP)

For a typical 28-day cycle:

$\text{Due Date}=\text{LMP}+280\text{ days}$

For a different average cycle length:

$\text{Due Date}=\text{LMP}+280+(C-28)\text{ days}$

Where (C) is the average menstrual cycle length.

Example: If your last period started on October 5, 2026:

Cycle-length adjustments assume ovulation timing changes with cycle length. Actual ovulation can vary, especially with irregular cycles.

2. Conception Date

If you know your estimated conception date:

$\text{Due Date}=\text{Conception Date}+266\text{ days}$

For example, conception on October 5, 2026, gives an estimated due date of June 28, 2027.

Conception dates are often approximate because fertilization timing may not be known precisely.

3. Known Due Date

If your healthcare professional has already established a due date, enter it using the Due date option.

The calculator estimates your current pregnancy week, trimester, and remaining time based on that date.

4. Ultrasound

Select Ultrasound and enter the scan date and gestational age reported on the ultrasound.

$\text{Due Date}=\text{Scan Date}+(280-\text{Gestational Age in Days})$

For example, an ultrasound on October 5, 2026, showing 12 weeks and 0 days gives an estimated due date of April 19, 2027.

Early ultrasound is generally more reliable for establishing pregnancy dates than later ultrasound. The calculator uses the gestational age you enter; it does not interpret ultrasound images.

5. IVF Transfer Date

For IVF pregnancies, the calculator uses the embryo transfer date and embryo age.

$\text{Due Date}=\text{Transfer Date}+266-\text{Embryo Age}$

For an October 5, 2026, transfer, the estimated due dates are June 25, June 23, and June 22, 2027, respectively.

For more information about pregnancy dating methods, see the ACOG guidance on estimating due dates.

How to Calculate Pregnancy Weeks and Months

Understanding how to calculate pregnancy weeks can help you follow your pregnancy progress.

Gestational age is measured in completed weeks and additional days. For example, 12w 3d means 12 completed weeks and 3 days.

For pregnancy dated from the last menstrual period:

$\text{Gestational Age in Days}=\text{Current Date}-\text{LMP}$

$\text{Completed Weeks}=\left\lfloor\frac{\text{Gestational Age in Days}}7\right\rfloor$

The remaining days are the days left after counting complete weeks.

For other dating methods, gestational age is calculated from the estimated pregnancy timeline.

Pregnancy Month Calculator by Week

Pregnancy is measured medically in weeks rather than months because calendar months have different lengths.

If you are looking for a pregnancy month calculator, the following table provides an approximate month-by-week reference.

These month groupings are approximate, not standardized medical boundaries.

Our calculator displays gestational age in weeks and days rather than providing a separate pregnancy-month result.

Pregnancy Weeks and Trimesters

Pregnancy is commonly divided into three trimesters.

Pregnancy is also classified by the timing of delivery:

Your estimated due date represents 40 weeks of pregnancy, but delivery may occur before or after that date.

If you are still pregnant after your due date, contact your maternity care team for guidance.

For clinical definitions, see the NICHD pregnancy terminology guide.

Understanding Your Pregnancy Tracker Results

The calculator displays several results to help you follow your estimated pregnancy timeline.

Due Date: The estimated date when pregnancy reaches 40 weeks.

Current Week: Your estimated gestational age in weeks and days.

Trimester: Your current pregnancy stage.

Weeks Remaining: The approximate number of weeks until your due date.

Likely Conception: An estimated conception date, not a confirmed date of fertilization.

Pregnancy Progress: A visual progress bar showing how far you are through the estimated 40-week timeline.

Days Since Last Period: The number of days since the entered or estimated start of pregnancy dating.

Days Remaining: The estimated number of days until the due date, or an overdue indicator when applicable.

Next Milestone: An estimated upcoming pregnancy event or developmental milestone.

Trimester Information: A summary of the three pregnancy stages.

Week-by-Week Schedule: A timeline of estimated pregnancy progress.

The pregnancy calculator week by week feature helps you explore upcoming stages, but development varies from one pregnancy to another. Milestones and fetal-size information are general estimates, not individual medical measurements.

How Accurate Is a Pregnancy Calculator?

A pregnancy calculator provides an estimated timeline rather than a confirmed delivery date.

Its accuracy depends on the information entered and the dating method used.

• Last period: Useful when menstrual dates are known and cycles are regular.

• Conception date: Helpful when conception timing is reasonably established.

• Ultrasound: Early ultrasound can provide reliable pregnancy dating.

• IVF transfer: Uses the known transfer date and embryo age.

• Known due date: Uses the date established by your healthcare professional.

Irregular cycles, uncertain menstrual dates, and variations in ovulation timing can affect the estimate.

A pregnancy calculator cannot confirm pregnancy, determine fetal health, or predict the exact delivery date.