Due Date Calculator
Estimate your pregnancy due date from your last period, conception, or IVF transfer date. See gestational age and trimesters - free and private.
Enter a date to estimate your due date.
Features
100% Browser-Based
Your pregnancy dates are never uploaded. All calculations run locally in your browser.
Free & No Sign Up
No account, no email, no limits. Medical dates stay on your device.
Instant Results
Due date, gestational age, and trimester update live as you enter or change dates.
Three Dating Methods
Calculate from your last period (with cycle-length adjustment), conception date, or IVF transfer date - including day-3 and day-5 embryos.
Milestone Timeline
See when each trimester ends, the viability window, and full term alongside your countdown.
How to Calculate Your Due Date?
- Choose a tab: last period (LMP), conception date, or IVF transfer.
- Enter the date - and your average cycle length if using LMP.
- Read your estimated due date and how many days remain.
- Check your current gestational age, trimester, and milestone dates below.
Common Use Cases
Early Pregnancy Dating
Convert a positive test and a remembered last period into an estimated due date before your first appointment.
IVF Pregnancy
Calculate from the exact embryo transfer date - day-3 and day-5 embryos both supported.
Tracking Progress
Revisit anytime to see how far along you are, which trimester you are in, and the days remaining.
Planning & Leave
Use the estimated date to plan maternity leave, travel, and family announcements.
Tips for Reading Your Due Date
- ✓ Think 'due week, not due day' - only about 4% of babies arrive exactly on their estimated date.
- ✓ An early ultrasound (before 12 weeks) is more accurate than any calendar method and may shift your date.
- ✓ Set the cycle-length field to your real average; assuming 28 days when yours are 34 shifts the estimate by nearly a week.
- ✓ Anything from 37 to 42 weeks of gestation counts as a normal, full-term delivery window.
Frequently Asked Questions
Is my pregnancy information sent to any server?
No. The due date calculator runs entirely in your browser using client-side JavaScript - the dates you enter and the results you see never leave your device. Pregnancy timing is deeply personal medical information that many people share selectively, sometimes not even with their workplace or extended family, so ToolsMio treats it with the same local-only policy as every other tool on the site. You can verify the claim yourself: open DevTools, switch to the Network tab, and enter your dates - not a single request is generated. Nothing is stored beyond your own browser's local storage, which simply refills the form on your next visit.
How is my due date calculated?
The default method is Naegele's rule: your due date is the first day of your last menstrual period (LMP) plus 280 days - 40 weeks - which assumes a 28-day cycle and ovulation on day 14. If your cycles run longer or shorter, the tool shifts the estimate accordingly, because ovulation generally happens about 14 days before your next period, not 14 after your last one. If you know your conception date, the tool counts 266 days (38 weeks) from it. For IVF pregnancies it counts backward from the transfer: a day-5 embryo is due 261 days after transfer, a day-3 embryo 263 days. Dating by an early ultrasound (before 12 weeks) remains the clinical gold standard and can supersede all of these.
How accurate is the estimated due date?
Treat it as a due week, not a due day. Even with perfectly regular cycles, only about 4% of babies arrive exactly on their estimated date; roughly 60% are born within a week of it, and full-term births naturally spread from 37 to 42 weeks. First pregnancies tend to run a few days longer than subsequent ones. This is why obstetric guidelines describe 39-40 weeks as 'term' and consider anything from 37 to 42 weeks normal. If your early ultrasound gives a different date than this calculator, your provider will usually trust the ultrasound, because it measures the embryo directly rather than inferring age from cycle dates.
How is gestational age different from conception age?
Gestational age counts from the first day of your last period - about two weeks before conception actually occurred - which is why a '40-week pregnancy' overlaps only 38 weeks of fetal development. Doctors, midwives, and every chart in your prenatal file use gestational age, and so does this tool: when it says you are 12 weeks and 3 days, that follows the same convention your clinic uses. Conception (or fetal) age is simply gestational age minus roughly two weeks. This standard exists because the LMP is usually a known date while conception is not, making gestational age the more practical anchor for scheduling scans and screening tests.
What if I don't know my last period or my cycles are irregular?
Use the Conception Date tab if you know when you conceived, or the IVF Transfer tab if this was an IVF pregnancy - in IVF cases the transfer date is exact, so that method is the most precise of the three. If none of the dates are known, an early ultrasound performed in the first trimester gives the most reliable estimate, and your provider can convert it to a due date for you. For irregular cycles, the LMP method with the cycle-length field set to your average still usually lands within a week or two. Bring whatever estimate you have to your first prenatal appointment and let the clinical dating refine it.