What to do after you get a positive pregnancy test?

Enter the first day of your last period to estimate your due date, current gestational age, and when to book your first prenatal visit.

Quick Facts

Naegele's rule
EDD = LMP + 280 days
Adjusted by (cycle length - 28) days for cycles other than 28 days.
Gestational age
Counted from your LMP, not conception
Ovulation and conception usually occur about 2 weeks after the LMP.
First prenatal visit
Often booked near 8 weeks
Many clinics schedule the first visit within a few weeks of a positive test.

Your Results

Calculated
Estimated due date
-
Naegele's rule, cycle-adjusted
Gestational age today
-
Weeks + days since LMP
Current trimester
-
Based on gestational age
First prenatal visit
-
Suggested scheduling window

Ready

Enter the first day of your last period to estimate your due date and next steps.

About this calculator

A positive pregnancy test confirms that hCG hormone is present, but it does not tell you your due date or where you are in the pregnancy. This calculator performs the standard obstetric calculation - Naegele's rule - to turn the first day of your last menstrual period into an estimated due date, your current gestational age, your trimester, and a target window for booking your first prenatal visit.

How the estimate is calculated

Naegele's rule estimates the due date as 280 days (40 weeks) after the first day of the last menstrual period (LMP). Because not everyone ovulates on day 14 of a 28-day cycle, this calculator adjusts the estimate by adding or subtracting the difference between your average cycle length and 28 days. Gestational age - the number obstetric care uses throughout pregnancy - is simply the number of days between the LMP and today, expressed in weeks and days. Estimated conception date is calculated as roughly (cycle length minus 14) days after the LMP.

What to do after a positive test

  • Confirm the result with your clinician or pharmacy, especially if the test was faint or you are unsure of the date.
  • Start (or continue) a prenatal vitamin containing folic acid, which is most protective in the earliest weeks.
  • Use your estimated due date and gestational age to schedule a first prenatal visit - most guidelines suggest booking within a few weeks, often around 8 weeks gestation.
  • Note any medications, supplements, or habits (alcohol, smoking, certain foods) to discuss with your provider at that first visit.

Limits of a date-based estimate

This calculation depends entirely on the accuracy of the LMP date and an assumed, regular cycle length. Irregular cycles, recent hormonal contraception, or an LMP you are unsure of can shift the true due date by a week or more. A first-trimester ultrasound, which measures the embryo directly, is generally considered more accurate than LMP dating alone and is commonly used to confirm or adjust the estimate.

Important disclaimer

This tool performs a standard dating calculation for planning purposes only. It does not diagnose pregnancy, assess viability, or replace clinical care. Confirm your pregnancy and due date with a qualified healthcare provider.

Frequently Asked Questions

What should I do right after a positive pregnancy test?
Confirm the result with your clinician (a blood test or a repeat urine test), start a prenatal vitamin with folic acid if you have not already, and work out your estimated due date and current gestational age from the first day of your last period. Most guidelines suggest booking a first prenatal visit within a few weeks, often around 8 weeks of gestation.
How is my due date calculated from a positive test?
The standard method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. Because ovulation shifts with cycle length, the estimate is commonly adjusted by adding or subtracting the difference between your average cycle length and 28 days. This gives an estimated due date; an early ultrasound can refine it further.
Why is gestational age counted from my last period instead of conception?
Obstetric convention counts pregnancy in weeks from the first day of the last menstrual period, not from conception, because the LMP date is usually known with more confidence than the exact day of conception. Conception typically happens about two weeks after the LMP, so a pregnancy dated at 4 weeks by this method is roughly 2 weeks past conception.

Related calculators