Use our Pregnancy Calculator to estimate your due date, current gestational age, trimester, and key milestones. Whether you know the first day of your last menstrual period (LMP), have a dating ultrasound, or know your conception date, this tool gives you a personalized pregnancy timeline in seconds.
How the Pregnancy Calculator works
The calculator uses well-established obstetric formulas to estimate your expected due date (EDD) and pregnancy progress. You can enter your LMP and average cycle length, provide a known conception or ovulation date, or use ultrasound measurements. The tool prioritizes ultrasound data (when available), then conception date, and finally LMP with cycle-length adjustments.
- LMP method: Calculates EDD as roughly 40 weeks (280 days) from your last period, with an adjustment for cycle length.
- Conception method: Uses fetal age to estimate a due date 266 days from conception/ovulation.
- Ultrasound method: Aligns your due date based on the gestational age measured at your scan.
LMP and cycle length
Many people rely on the first day of the last menstrual period to estimate pregnancy dates. If your cycles are not the standard 28 days, adjusting the cycle length can better reflect when you likely ovulated. Longer cycles typically push your due date later, while shorter cycles bring it forward.
Using a dating ultrasound
Early ultrasounds are among the most accurate ways to date a pregnancy. If you enter the ultrasound date and the gestational age shown on your report, the calculator will anchor your due date to that measurement. This is particularly helpful for irregular cycles or uncertain LMP dates.
Conception or IVF date
If you know your ovulation date or had an IVF embryo transfer, you can use that precise timing to estimate your due date. The calculator assumes a typical 266 days from conception to birth, aligning with clinical standards.
What your results include
- Estimated Due Date (EDD)
- Current gestational age in weeks and days
- Your current trimester
- Key milestones like 12, 20, and 28 weeks
- Full-term window (37–42 weeks)
- An estimated conception window
Accuracy and what to expect
Remember, due dates are estimates. Only a small percentage of babies arrive exactly on the EDD. The full-term window spans from 37 weeks (early term) to 42 weeks (post-term). Ultrasound dating in the first trimester is generally more accurate than LMP alone, especially if your cycles vary.
If your calculated due date differs from your provider’s estimate, they may be using ultrasound measurements or additional clinical factors. Always discuss your results with your healthcare team if you have concerns.
Tips for using the Pregnancy Calculator
- Enter the most accurate LMP date you have; if unsure, use your best estimate.
- Adjust cycle length if your cycles are commonly shorter or longer than 28 days.
- If you have an early ultrasound, use the ultrasound date and measured gestational age.
- For IVF or tracked ovulation, enter your conception date to refine your EDD.
- Recheck your results as new information (like a scan) becomes available.
When to seek medical advice
This tool provides general estimates and educational guidance. It does not diagnose, and it isn’t a substitute for professional care. Contact your healthcare provider for personalized advice, especially if you have symptoms, questions about your dates, or a history of irregular cycles.