How do I calculate how far along I am?

Bottom lineCalculate how far along you are by counting the weeks from the first day of your last menstrual period to today, since pregnancy is dated from the LMP (about two weeks before conception) and lasts roughly 40 weeks; dating is less reliable with irregular cycles or an unknown LMP, so an early ultrasound gives the most accurate estimate.

Pregnancy is usually dated from the first day of your last menstrual period (LMP), not from conception - which makes you about two weeks "pregnant" before you actually conceived. This is the standard clinicians use.

The simple method

1. Find the first day of your last period
2. Count the weeks from that date to today
3. That number is how many weeks pregnant you are

For example, if your last period started 8 weeks ago, you're around 8 weeks pregnant.

Why LMP dating is used

The LMP is a reliable, known date, while the exact conception day is usually uncertain. Pregnancy lasts about 40 weeks from the LMP.

When dates are adjusted

• If your cycles are irregular or you don't know your LMP, dating is less reliable
• An early ultrasound (especially in the first trimester) gives the most accurate dating and may revise the estimate

Due date

Your due date is roughly 40 weeks from your LMP. Only about 1 in 20 babies arrive on the exact date, so treat it as an estimate.

Femora uses your last period date to estimate how far along you are and your due date.

Estimate it: pregnancy week calculator