pregnancy calculator by conception date

How this pregnancy calculator by conception date works

This calculator estimates your due date from the day conception occurred. In clinical pregnancy dating, providers usually count from the first day of your last menstrual period (LMP), which is about two weeks before conception for many people. That means:

• Conception-based due date: conception date + 266 days (38 weeks)
• LMP-based due date: LMP date + 280 days (40 weeks)

Both methods usually point to the same expected delivery window when ovulation timing is average. This tool also gives a practical snapshot of where you are right now in the pregnancy timeline.

Why use conception date instead of LMP?

Using conception date can be useful when:

• You tracked ovulation with LH strips, BBT, or fertility apps.
• You conceived via IUI, IVF, or timed intercourse and know the likely fertilization date.
• Your cycles are irregular and LMP dating is less reliable.

That said, your healthcare provider may still use early ultrasound to confirm or adjust dating if needed.

What your results mean

Estimated due date (EDD)

Your EDD is the best estimate of when birth might occur. Most babies are born within a range around that date, not exactly on it.

Gestational age

This is the standard “weeks pregnant” number used in prenatal care. It is generally counted from LMP, not conception. So if conception happened 10 weeks ago, gestational age is typically around 12 weeks.

Fetal age

Fetal age starts at conception. It is usually about two weeks less than gestational age when using standard cycle timing.

Trimester

• First trimester: 0 to 13 weeks + 6 days
• Second trimester: 14 to 27 weeks + 6 days
• Third trimester: 28 weeks to birth

Common pregnancy milestones to watch for

• 6–8 weeks: early prenatal confirmation visit
• 10–13 weeks: optional genetic screening window
• 18–22 weeks: anatomy ultrasound
• 24–28 weeks: glucose screening
• 35–37 weeks: Group B strep test
• 39–40 weeks: full-term window and delivery planning

Frequently asked questions

Is this due date exact?

No. It is an estimate. Only a small percentage of births happen on the exact due date.

What if I don’t know my exact conception date?

Use your LMP date or ask your provider for dating guidance based on ultrasound. If conception timing is uncertain, LMP-only calculations can drift.

Can ovulation happen earlier or later than day 14?

Yes. That’s why this calculator allows you to adjust “days from LMP to conception.” If you know your ovulation pattern, update that value for a better estimate.

Does IVF change due date calculations?

IVF pregnancies are often dated using embryo transfer date and embryo age, which can be very precise. Use clinic-provided dating as your primary reference.