Conception & Due Date Calculator
Instantly estimate your conception date, current gestational age, and baby’s due date. Free, accurate tool based on your last menstrual period or known ovulation.
Calculate Your Key Dates
Enter the first day of your last menstrual period or your known conception date to get an instant, personalised evaluation of your pregnancy timeline.
Pregnancy Details
Enter your dates to calculate your estimated timeline
Timeline Evaluation
Estimated conception, due date, and current progress
Pregnancy Trimesters
A standard full-term pregnancy lasts about 40 weeks (280 days) from the first day of the last menstrual period.
| Trimester | Weeks | Key Developments | Typical Scans |
|---|---|---|---|
| First Trimester | Weeks 1 – 13 | Major organs form, heartbeat detectable | Dating scan (8-14 weeks) |
| Second Trimester | Weeks 14 – 27 | Movement felt, anatomy develops rapidly | Anomaly scan (18-21 weeks) |
| Third Trimester | Weeks 28 – 40+ | Rapid weight gain, lungs mature, positioning | Growth scans (if required) |
Conception & Pregnancy FAQ
Everything you need to know about calculating conception dates, due dates, and pregnancy milestones.
The estimated due date (EDD) is typically calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). If you know your exact conception or ovulation date, 266 days (38 weeks) are added to that date instead.
The Last Menstrual Period (LMP) is the first day of your last period. Conception occurs later, typically around 14 days before your next expected period (ovulation). Medical professionals use LMP to calculate pregnancy because it is a more definite and observable date than conception.
A conception calculator provides a highly accurate estimate for women with regular 28-day cycles. However, only about 4% of women deliver on their exact due date. Ultrasound scans in the first trimester are considered the most accurate method for dating a pregnancy.
Yes, first-trimester ultrasounds (particularly between 8 and 13 weeks) measure the baby’s crown-rump length (CRL) to estimate gestational age with an accuracy of about ±5 days. Your midwife or doctor can use this scan date to retrospectively estimate your conception date.