Pregnancy Week Calculator
Find out how many weeks pregnant you are from your last period, a conception date, or a known due date, with the current trimester, due date, and progress.
Count from
Calculated in your browser. Nothing is uploaded.
Enter the first day of your last period to see how far along you are.
How to calculate how many weeks pregnant you are
Choose what date you know
Pick counting from your last period, a conception date, or a due date already given to you.
Enter the date
Type that date. For the last period method, you can also adjust the cycle length away from the default 28 days.
Read your current week
See your gestational age in weeks and days, the trimester, the estimated due date, and how far through the pregnancy you are.
Copy the summary
Click Copy summary to save the current week, due date, and days remaining as plain text.
Why use this tool
Three ways to count
Enter the first day of your last period, an estimated conception date, or a due date already given to you, and the tool works out the same picture from any of them.
Current week, to the day
See gestational age in weeks and days, the current trimester, and a progress bar showing how far through a typical 40-week pregnancy you are.
Due date and days remaining
Alongside the current week, get the estimated due date and a plain count of days to go, or days past due if the date has passed.
A neutral note for the current week
Each week comes with one short, factual sentence about that stage, hedged appropriately since every pregnancy is different.
Cycle length adjustment
When counting from the last period, adjust the cycle length away from the standard 28 days to shift the due date and gestational age to match.
Runs entirely in your browser
Every calculation happens on your device. Nothing you enter is uploaded.
About this tool
This calculator answers how many weeks pregnant someone is, using whichever date is easiest to enter. Counting from the first day of the last period is the standard clinical method and follows the usual 40-week, 280-day rule, adjusted for a cycle length other than 28 days. Counting from an estimated conception date works back to an implied last period assuming ovulation around day 14 of a standard cycle. Counting from a due date already given by a care provider works backward from that date instead, which is useful when you know the due date but not the exact date it was based on.
Whichever method is used, the result shows the same set of figures: gestational age in weeks and days, the current trimester, the estimated due date, days remaining or days past due, and what share of a typical pregnancy has passed. A short, factual sentence notes what is generally true of that week, phrased carefully since timing varies between pregnancies. To estimate a due date from the last period alone, the due date calculator covers the same ground with more milestone detail, and the ovulation calculator estimates a fertile window instead. For working out age from a birth date once the baby has arrived, the age calculator handles that.
Every figure here is an estimate, not a diagnosis, and this is not medical advice. Only a small share of pregnancies deliver on the exact estimated due date, and a clinical dating scan from a care provider is more accurate than any date-based calculator. All calculations run in your browser, and the dates you enter are never uploaded, stored, or logged.
Frequently asked questions
- How many weeks pregnant am I calculated?
- From whichever date you enter, the tool works out the first day of the last menstrual period, either directly, or by working back from a conception date or a due date. It then measures the days from that implied last period to today and expresses it in weeks and days.
- What is the difference between the three counting methods?
- Counting from the last period is the standard method and lets you adjust for a cycle length other than 28 days. Counting from a conception date assumes ovulation around day 14 of a standard cycle. Counting from a known due date works backward using the standard 280-day pregnancy length, which is useful if a care provider already gave you a due date.
- Why does cycle length matter for the last period method?
- The standard 40-week estimate assumes ovulation around day 14 of a 28-day cycle. A longer or shorter cycle shifts ovulation and conception earlier or later, so the tool adjusts the due date and gestational age by the same number of days.
- Is this an accurate way to know how far along I am?
- It is a well-established estimate based on standard dating rules, not a medical measurement. An ultrasound dating scan from a care provider is more accurate, especially early in pregnancy, and should be used to confirm or adjust any estimate from a calculator.
- Is this medical advice?
- No. This tool provides a date-based estimate only. It is not medical advice, and any question about a pregnancy should go to a qualified care provider.
- Is my data uploaded anywhere?
- No. Every date you enter is processed in your browser and never sent to a server, stored, or logged.
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