Calculator Comparison

Conception Date Calculator vs Due Date Calculator

Not sure which calculator to use? Here's a side-by-side comparison of the Conception Date Calculator and Due Date Calculator to help you pick the right one for your needs.

Conception Date Calculator

Pregnancy & Baby

Estimate your conception date based on your due date or last menstrual period to determine when pregnancy began.

What you enter

Calculate Based On
Date

What you get

Estimated Conception Date(primary)
Conception Window
Current Gestational Age

Use Conception Date Calculator

Due Date Calculator

Pregnancy & Baby

Calculate your estimated due date using your last menstrual period, conception date, or IVF transfer date.

What you enter

Calculate Based On
Date

What you get

Estimated Due Date(primary)
Estimated Conception Date
Current Week of Pregnancy
Days Until Due Date

Use Due Date Calculator

Key Differences

Feature	Conception Date Calculator	Due Date Calculator
Category	Pregnancy & Baby	Pregnancy & Baby
Inputs	2 required fields	2 required fields
Outputs	3 results	4 results
Chart	No chart	No chart
FAQs	3 answered	3 answered

Input Comparison

Shared Inputs

Calculate Based On
Date

Only in Due Date Calculator

Average Cycle Length (for LMP)

Which Calculator Should You Use?

Use the Conception Date Calculator if you need to:

Calculate estimated conception date
When you know your calculate based on and date

Use the Due Date Calculator if you need to:

Calculate estimated due date
When you know your calculate based on and date

Frequently Asked Questions

How is the conception date calculated?

Conception typically occurs about 14 days after the first day of your last period (during ovulation). From a due date, subtract 266 days (38 weeks) to estimate the conception date.

Can I know the exact day of conception?

Not exactly. Conception can occur within a window of several days because sperm can survive up to 5 days and the egg lives for 12-24 hours after ovulation.

How is the due date calculated?

The most common method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period. Adjustments are made for cycle lengths that differ from 28 days.

How accurate is a due date?

Only about 5% of babies are born on their exact due date. Most babies arrive within 2 weeks before or after the due date. First-time mothers tend to deliver slightly later.

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Conception Date Calculator vs Fertility Calculator

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Due Date Calculator vs Pregnancy Calculator

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Due Date Calculator vs Pregnancy Week Calculator

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Bottom Line

Choose the Conception Date Calculator if you need to calculate estimated conception date. Use the Due Date Calculator if you need to calculate estimated due date. Both calculators are free and require no sign-up.

Use Conception Date Calculator Use Due Date Calculator

Feature

Conception Date Calculator

Due Date Calculator