Last updated: March 2026
Figuring Out How Far Along You Are
"How far along am I?" is one of the first questions every expectant parent asks. The answer depends on your last menstrual period (LMP) or your estimated due date, and the counting system can be surprisingly confusing at first.
Pregnancy is measured in gestational weeks starting from the first day of your last period — not from the day you conceived. This means that during "week 1" and "week 2," conception has not even happened yet. By the time most people get a positive pregnancy test (around the time of a missed period), they are already considered approximately 4 weeks pregnant.
If you know your due date from your doctor or an ultrasound, this calculator works backward to determine your current week. If you know your LMP, it calculates forward. Both methods give the same result when your dates are accurate.
An early ultrasound (typically between weeks 8-12) is the most accurate way to date a pregnancy. The earlier the ultrasound, the more precise the dating — first-trimester measurements are accurate to within about 5 days. If your doctor adjusts your due date after an ultrasound, use the updated date for the best accuracy.
Your pregnancy week matters because it determines which developmental milestones your baby has reached, which tests and screenings are due, and how close you are to key thresholds like viability (24 weeks) and full term (37 weeks).
Remember that every pregnancy progresses at its own pace. The week-by-week milestones and size comparisons are averages — your baby may be slightly ahead or behind, and that is perfectly normal. Your healthcare provider is the best resource for assessing your individual pregnancy.
Frequently Asked Questions
How do I figure out how far along I am?
The easiest method is to count from the first day of your last menstrual period (LMP). Pregnancy weeks start from that date — not from conception. If you know your due date, subtract it by 280 days to find the equivalent LMP, then count forward to today. Enter either date above to see your exact week and day.
I don't know my exact last period date. What do I do?
If you know your due date from an ultrasound or your doctor, use that instead — select the 'I know my due date' tab. An early ultrasound (before 12 weeks) is very accurate for dating. Your doctor can also estimate your gestational age at any appointment.
Why am I told I'm 2 weeks further along than I expected?
Pregnancy dating starts from your last menstrual period, which is about 2 weeks before ovulation and conception. So when you first miss your period and get a positive test, you're already considered about 4 weeks pregnant — even though conception was only about 2 weeks ago.
Is my baby really the size of that fruit?
The fruit comparisons are fun approximations to help visualize growth. Actual baby sizes vary — some babies are naturally larger or smaller at any given week. Your healthcare provider tracks growth through ultrasound and fundal height measurements.
What's the difference between weeks and months of pregnancy?
Pregnancy months don't map perfectly to calendar months because months vary in length. Roughly: months 1-3 are the first trimester (weeks 1-12), months 4-6 are the second trimester (weeks 13-27), and months 7-9 are the third trimester (weeks 28-40). At 40 weeks, you're about 9 months and 1 week pregnant.