Due Date Calculator
Due date = LMP + 280 days (Naegele's rule)Jan 15 + 280 days ≈ Oct 22, 2026
Free online tool
Due Date Calculator
Enter the first day of your last menstrual period to find your estimated delivery date.
Instant calculation
Due Date Calculator
Enter the first day of your last menstrual period to find your estimated delivery date.
Your result
Calculation
Your numbers stay in this browser. Nothing is uploaded or saved.
Three clear steps
How to use this calculator
- 01
Enter LMP date
Type the year, month and day of your last period.
- 02
Calculate
See your estimated due date.
- 03
Note
This is an estimate. Only about 5% of babies arrive on their due date.
The formula
How this calculation works
Add 40 weeks (280 days) to the first day of the last menstrual period.
Check the method
Worked examples
Each example follows the same formula used by the calculator.
LMP Jan 15, 2026 — due date?
Jan 15 + 280 days ≈ Oct 22, 2026≈ October 22, 2026Common questions
Questions about this calculation
What is the Due Date Calculator?
The Due Date Calculator helps you calculate your estimated pregnancy due date from your last period. Enter your values and select Calculate to get an instant result.
How is the result calculated?
Add 40 weeks (280 days) to the first day of the last menstrual period.
Can you show an example?
Example: LMP Jan 15, 2026 — due date? — ≈ October 22, 2026.
Is my data saved when I use the Due Date Calculator?
No. All calculations run locally in your browser. Your inputs and results are never uploaded, stored or shared with anyone.
Is the Due Date Calculator free to use?
Yes. The Due Date Calculator is completely free. No account, sign-up or payment is required. It works on mobile, tablet and desktop.
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