A pregnancy week calculator helps expectant parents determine their due date, current pregnancy week, and trimester from the first day of their last menstrual period (LMP). Tracking your pregnancy week by week lets you follow your baby's development milestones, plan prenatal appointments, and prepare for delivery with a clear countdown of days remaining.
Enter Your Dates
Due Date
--
Current Week
--
Trimester
--
Days Remaining
--
Estimated Conception Date
--
Trimester Progress
Key Milestones
First Heartbeat
Week 6 — --
Gender Reveal Possible
Week 18-22 — --
Viability
Week 24 — --
Full Term
Week 39 — --
Week-by-Week Development
Your current week is highlighted. Scroll to see all 40 weeks.
How to Use the Pregnancy Week Calculator
Tracking your pregnancy week by week is one of the most exciting parts of expecting a baby. This free pregnancy week calculator helps you determine your due date, identify which trimester you are in, and follow key developmental milestones from conception to delivery. Whether you are newly pregnant or approaching your due date, this tool gives you a clear picture of where you are in your pregnancy journey.
Step 1: Choose Your Input Method
The calculator offers two modes. If you know the first day of your last menstrual period (LMP), select the LMP mode and enter that date. This is the most common method used by healthcare providers to estimate a due date. If your doctor has already given you a due date based on an ultrasound, select the due date mode and enter that date instead. The calculator will work backward to estimate your conception date and current pregnancy week.
Step 2: View Your Due Date and Current Week
After entering your date and clicking Calculate, the tool displays four key results: your estimated due date, your current pregnancy week and day, which trimester you are in, and the number of days remaining until your due date. The due date is calculated using Naegele's rule, adding 280 days (40 weeks) to your LMP date. Keep in mind that only about five percent of babies arrive on their exact due date, so think of it as an estimated target rather than a guaranteed delivery day.
Step 3: Track Your Trimester Progress
The trimester progress section shows visual progress bars for each of the three trimesters. The first trimester covers weeks 1 through 13, the second trimester spans weeks 14 through 27, and the third trimester runs from week 28 through 40. An overall pregnancy progress bar shows your total percentage from start to due date. This makes it easy to see at a glance how far along you are in your pregnancy.
Step 4: Follow Key Milestones
The milestones section highlights four important moments in pregnancy: the first heartbeat around week 6, when gender can be determined between weeks 18 and 22, the point of viability at week 24, and full term at week 39. Each milestone shows the estimated date it will occur based on your LMP. Milestones you have already passed are highlighted in rose, giving you a satisfying visual of your progress. The week-by-week development section provides brief descriptions of baby growth for all 40 weeks, with your current week clearly marked.
Step 5: Share or Save Your Results
Since this pregnancy calculator runs entirely in your browser, your personal data is never stored or transmitted. You can take a screenshot of your results to share with your partner, family, or healthcare provider. Bookmark this page and return any time to recalculate as your pregnancy progresses. The tool is completely free, requires no account, and works on both desktop and mobile devices.
For a detailed walkthrough, see our guide: Pregnancy Week by Week Milestones.
For a detailed walkthrough, see our guide: First Trimester Guide: What Happens in Weeks 4-13.
FAQ
Is this pregnancy calculator free to use?
Yes, the Pregnancy Week Calculator is completely free with no limits. You can calculate due dates and track pregnancy progress as many times as you want. There is no signup required and no premium tier. Everything runs locally in your browser.
Is my pregnancy data safe and private?
Yes, everything runs entirely in your browser using client-side JavaScript. Your dates are never sent to a server, never stored in a database, and never shared with anyone. Once you close the page, your data is gone. There is no tracking of the information you enter.
How is the due date calculated from my last menstrual period?
The due date is calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is the standard method used by most healthcare providers. It assumes a regular 28-day cycle and that conception occurred around day 14. Your actual due date may vary based on individual cycle length and ultrasound findings.
How accurate is this pregnancy due date calculator?
This calculator uses the same Naegele's rule formula that doctors and midwives use for initial due date estimates. However, only about 5% of babies are born on their exact due date. Most babies arrive within two weeks before or after the estimated date. An early ultrasound measurement is typically the most accurate way to confirm your due date.
What are the three trimesters of pregnancy?
The first trimester spans weeks 1 through 13, covering early development including the formation of major organs. The second trimester runs from week 14 through 27, when the baby grows rapidly and you may feel movement. The third trimester covers weeks 28 through 40, as the baby gains weight and prepares for birth.
When can I find out the gender of my baby?
Most parents can learn their baby's gender through ultrasound between weeks 18 and 22, typically at the anatomy scan appointment. Some blood tests like NIPT (non-invasive prenatal testing) can reveal gender as early as week 10. This calculator highlights the gender reveal window as one of the key pregnancy milestones.
What does viability mean in pregnancy?
Viability refers to the point at which a baby could potentially survive outside the womb with medical support. This is generally considered to be around 24 weeks of pregnancy. Survival rates improve significantly with each additional week of gestation. Modern neonatal intensive care has pushed the boundary of viability earlier, but outcomes are best when babies reach full term at 39 to 40 weeks.
Can I use this calculator if I already know my due date?
Yes, the calculator has a reverse mode where you can enter your known due date to calculate your estimated conception date, current pregnancy week, and trimester. This is useful if your doctor has given you a due date based on an ultrasound and you want to track your weekly progress and upcoming milestones.