How to Use the Reverse Due Date Calculator

1. Enter your estimated due date.
2. Click Calculate Conception Date.
3. The tool subtracts 266 days (38 weeks) from your due date and shows your estimated conception date.

This calculator is helpful for anyone wanting to quickly figure out:

• “When did I get pregnant?”
• “What day did I conceive based on my due date?”
• “How far along was I on a certain date?”

Everything is based on simple date math.

FAQ

How is the conception date calculated?

The calculator subtracts 266 days (38 weeks) from your due date. This is the standard conception to birth timeline used in pregnancy date math.

Why 266 days instead of 280?

280 days includes the two weeks before ovulation.
266 days represents the actual conception window, which is why it’s used for reverse due date math.

Is this the same as figuring out ovulation?

Not exactly. This tool estimates conception based on your due date. Ovulation calculators estimate fertile days based on cycle length.

Does this give a medically verified conception date?

No — this is a date math calculator only, not medical advice. It simply subtracts 266 days from your due date.

Can this help with pregnancy timelines?

Yes. Many people use this tool for:

• “conception date from due date”
• “reverse pregnancy calculator”
• “when did I get pregnant based on due date”

It’s a quick way to map out pregnancy dates using simple math.