Free Conception Date Calculator
Estimate a conception date from the first day of the last menstrual period or an established due date.
Conception Date Calculator
Enter a value to begin.
How to use this conception date calculator
- Choose which date you know, enter it and calculate the conventional conception estimate.
- Check the inputs and preview, then use the primary action.
- Download, copy or use the result shown by the tool.
How the result is calculated
From LMP, the estimate adds 14 days and the related due date adds 280 days. From an established due date, it subtracts 266 days. ACOG explains that LMP dating assumes a 28-day cycle with ovulation on day 14 and that actual ovulation, conception and clinical dating can differ.
Method source: ACOG guidance on estimating a due date.
All calculation and transformation work happens in this browser tab. No entered value is sent to an Noler Tools application server.
Important limitations
Results are provided for convenience and should be checked independently before an important decision. A format or checksum result never authenticates an identity, document, account, licence, vehicle or registration.
Health limitation: This is a general educational estimate, not medical advice, diagnosis or a substitute for care from a qualified clinician. Do not use it to make treatment, nutrition, pregnancy or emergency-care decisions.
Frequently asked questions
Is this conception date calculator free?
Yes. It is free to use and does not require an account.
Does Noler Tools save my input?
No. The input and result remain in temporary browser memory and are not uploaded or saved by this site.