Pregnancy Due Date Calculator
Estimate due date from your last menstrual period.
🤰 Naegele's rule: due date = LMP + 280 days. Only an estimate — only 5% of babies arrive on their due date.
What Is This Tool?
This calculator estimates your pregnancy due date using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. It also shows the likely conception date and current week.
The 40-Week Framework
Pregnancy is counted in weeks from the last period, not from conception. The "40 weeks" includes ~2 weeks before you actually conceived. Full term is anywhere from 37 to 42 weeks.
Trimesters
- First trimester: Weeks 1-13 (organ development)
- Second trimester: Weeks 14-27 (growth, movement felt)
- Third trimester: Weeks 28-40+ (final growth, preparation for birth)
Only an Estimate
Only about 5% of babies arrive on their estimated due date. Most arrive within two weeks of it. First babies tend to arrive a few days late; subsequent babies often come earlier.
Frequently Asked Questions
What if my cycles are irregular?
Naegele's rule assumes a 28-day cycle with ovulation on day 14. If your cycles are longer or shorter, an early ultrasound (before 12 weeks) provides a more accurate due date.
About the Pregnancy Due Date Calculator
The Pregnancy Due Date Calculator lets you figure out due date calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
How to Use This Tool
- Enter the main values the calculator asks for (for example, amount, rate, and time).
- Pick the right unit or option where the tool offers a choice.
- Read the result, which appears instantly below the inputs.
- Adjust any field to test a different scenario — the answer updates without a reload.
- Copy or note the result. Nothing is stored, so close the tab when you're done.
Why Use an Online Calculator?
Browser-based tools like this one have a few real advantages over installed software or manual methods:
- No installation. It opens instantly in any browser, on any operating system.
- Private by default. Everything runs locally, so your data stays on your device.
- Always up to date.There's nothing to update — you always get the latest version when you load the page.
- Free and unlimited. Use it as often as you like, with no account and no caps.
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