This pregnancy conception calculator estimates the date of conception and due date based on your last menstrual period (LMP) and cycle length. By adjusting for ovulation, it provides a more accurate pregnancy timeline for planning and learning.
- Conception date: estimated from LMP and ovulation window.
- Due date: calculated as 40 weeks (280 days) from LMP.
- Ovulation day: usually 14 days before your next period.
- Trimester timeline: shows week-by-week progress from conception to delivery.
- Cycle length adjustment: supports cycles from 21–35 days for more precise results.
How to use: Enter the first day of your last menstrual period, your average cycle length, and optional ovulation date if known. The calculator will show estimated conception date, due date, and trimester breakdown.
Common searches: conception calculator by due date, pregnancy calculator from LMP, when did I conceive, pregnancy due date estimator.
Pregnancy Conception Calculator
Estimate your conception and due dates based on your last menstrual period and cycle length.
How the conception calculator works
The conception calculator estimates the date you conceived by counting forward from your last menstrual period and adjusting for ovulation. Most pregnancies last about 280 days (40 weeks) from the first day of the LMP. If you know your average cycle length, the calculator adjusts ovulation timing to improve accuracy.
Conception date vs. due date
Conception date is the estimated day when sperm fertilised the egg. Due date is 40 weeks from the LMP and represents the expected time of delivery. Both are estimates—only a small percentage of babies are born on the exact due date.
Trimester breakdown
Pregnancy is divided into three trimesters, each with key developmental milestones:
| Trimester | Weeks | Timeline |
|---|---|---|
| First | 1–13 | Conception to end of 13th week |
| Second | 14–27 | Rapid growth, often easiest stage |
| Third | 28–40 | Final development until delivery |
Factors that affect conception timing
- Cycle length: shorter or longer cycles shift ovulation earlier or later.
- Ovulation variability: stress, illness, or lifestyle changes can affect timing.
- Fertilisation window: sperm can survive up to 5 days, so conception may occur a few days after intercourse.
Why this calculator is useful
This tool is designed for planning, education, and understanding pregnancy timelines. Expecting parents can estimate conception for personal records, while students can use it to understand how due dates are calculated in biology and health sciences.
Pregnancy Conception Calculator FAQs
No. Conception is usually estimated based on LMP and ovulation. Because sperm can live for up to 5 days, the exact day is hard to confirm without medical testing.
Doctors may adjust due dates after ultrasounds, which can more accurately measure the baby’s development compared to LMP calculations.
It is typically 280 days (40 weeks) from the first day of the last menstrual period. The calculator uses this standard formula with cycle length adjustments.
Yes. Shorter or longer cycles shift the expected ovulation and conception date. The calculator allows input of cycle length for better accuracy.
No. This tool only estimates dates for learning and planning. A healthcare professional and medical tests are required to confirm pregnancy.
Conception may happen on the day of ovulation or a few days later, since sperm can survive in the reproductive tract for several days.