Due Date Calculator
Estimate your due date & current week.
100% private — runs in your browser, nothing is uploaded.
Estimated due date
Sunday, February 14, 2027
You are currently
10w 0d
Trimester
First
Days until due date
210
An estimate only — about 1 in 20 babies arrive on the exact due date. Always confirm dates with your healthcare provider. Nothing you enter leaves your browser.
How to use the Due Date Calculator
- 1Pick a starting point
Last menstrual period (most common) or conception date.
- 2Enter the date
Select the date from the calendar field.
- 3Adjust cycle length
In LMP mode, set your average cycle if it isn't 28 days.
- 4Read the results
See the due date, current week, trimester and days to go.
Examples
| Input | Output |
|---|---|
LMP Jan 1, 28-day cycle | due Oct 8 (same year) |
LMP Jan 1, 31-day cycle | due Oct 11 (+3 days) |
Estimate your due date in seconds
This pregnancy due date calculator estimates when your baby is likely to arrive using the same rule clinicians use: 280 days from the first day of your last menstrual period, adjusted for your cycle length — or 266 days from conception if you know that date. It also shows how many weeks pregnant you are today, your current trimester and the days remaining.
Why “40 weeks” includes two weeks you weren't pregnant
Gestational age is counted from the last period because that date is known reliably, while ovulation usually happens about two weeks later. So “8 weeks pregnant” typically means about 6 weeks since conception. Cycle length matters too: longer cycles usually mean later ovulation, which the calculator corrects for automatically.
An estimate, not a schedule
Due dates set expectations, not appointments — the large majority of births happen in the two weeks around the date rather than on it, and an early ultrasound may shift your official date. Use this tool for planning, and rely on your healthcare provider for medical decisions. For related date math, see the date difference calculator and the age calculator.
Frequently Asked Questions
How is a due date calculated?
The standard method (Naegele's rule) adds 280 days — 40 weeks — to the first day of your last menstrual period. If you know the conception date instead, 266 days are added. This tool supports both.
Why count from the last period and not conception?
Most people know their last period's date far more reliably than the conception date, so medicine standardized on LMP. That's also why 'weeks pregnant' includes about two weeks before conception happened.
What if my cycle isn't 28 days?
Ovulation shifts with cycle length, so the tool adjusts: with a 31-day cycle the due date moves 3 days later than the standard rule. Enter your average cycle length for a better estimate.
How accurate are due dates?
They're estimates — only about 1 in 20 babies is born on the exact due date, and most arrive within two weeks either side. A first-trimester ultrasound gives the most accurate dating.
When does each trimester start?
Conventionally: first trimester weeks 1–12, second weeks 13–26, third week 27 to birth. The calculator shows your current week and trimester automatically.
Is my information private?
Completely. The dates you enter are processed locally in your browser and never uploaded or stored.