Week 20
2nd Trimester
2026-06-15
139 days
A due date is the estimated day your baby may arrive. It usually marks 40 weeks of pregnancy, counted from the first day of your last menstrual period (LMP). Your actual birth date can differ because pregnancy length varies for many pregnancies.
Our Due Date Calculator quickly estimates your baby's expected due date and shows key pregnancy dates using common dating methods.
Choose LMP, conception, IVF, or ultrasound.
Enter the relevant date into the calculator.
Get the due date, current week, trimester, and days remaining.
Copy the calculated pregnancy details for future use.
Choose LMP, conception, IVF, or ultrasound.
Enter the relevant date into the calculator.
Get the due date, current week, trimester, and days remaining.
Copy the calculated pregnancy details for future use.
Your results show the estimated due date, EDD, gestational age, trimester, estimated conception date, and days remaining.
Your estimated due date is the expected delivery date based on your selected dating method and the pregnancy information you entered.
Gestational age shows how many weeks and days have passed since the first day of your LMP. It helps track pregnancy timing.
Your trimester shows the current stage of pregnancy based on gestational age. It helps place fetal development within the pregnancy timeline.
The estimated conception date shows when fertilization most likely occurred. The calculator estimates it from your selected dating method.
Days until due date shows the approximate time remaining before your estimated delivery date. It can help you track pregnancy timing.
Naegele's Rule
Due Date Formula: .
Step by step guide
Practical Example
If your LMP began on January 1, the standard estimate adds 280 days. The estimated due date falls around October 8. This example assumes a regular 28 day cycle.
No single method fits every pregnancy. LMP works well with regular cycles, while early ultrasound often helps when dates remain uncertain.
LMP dating uses the first day of the last menstrual period and usually adds 280 days. It works best with a known LMP and regular cycles.
Conception dating starts with a known conception date and adds about 266 days. It can help when the conception date is known more closely.
IVF dating uses embryo transfer or treatment dates because conception timing is known more closely. Day 3 and Day 5 transfers use different calculations.
Ultrasound dating uses fetal measurements to estimate gestational age. Early scans can provide stronger dating when LMP information seems uncertain.
Ultrasound dating can help when LMP information lacks accuracy, especially with irregular cycles or an unknown last menstrual period.
Early pregnancy ultrasound can give a more reliable gestational age estimate, especially before later pregnancy growth creates wider dating variation.
Ultrasound can help when irregular cycles make LMP dating less reliable because ovulation may not occur around day 14 each cycle.
When you cannot recall your LMP, an early ultrasound can help establish pregnancy dating and provide a clearer gestational age estimate.
A 28 day cycle forms the standard LMP estimate. Longer or shorter cycles can shift ovulation and change the estimated due date.
A longer menstrual cycle can shift ovulation later, so your due date may move later than the standard 28 day LMP estimate for most pregnancies.
A shorter menstrual cycle can shift ovulation earlier, so your due date may move earlier than the standard 28 day LMP estimate.
Irregular periods can make LMP dating less reliable because ovulation may vary from month to month and cycle length can change.
Gestational age counts from the LMP, while fetal age counts from conception. The two measures differ by about two weeks.
Gestational age counts pregnancy from the first day of the LMP. It helps clinicians describe pregnancy weeks and track fetal development.
Fetal age, or conceptional age, counts from conception. It usually measures about two weeks less than gestational age.
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These answers explain pregnancy length, dating methods, due date accuracy, IVF, ultrasound, gestational age, and LMP formulas.