Calculator Comparison

Due Date Calculator vs Ovulation Calculator

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

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

Ovulation Calculator

Pregnancy & Baby

Calculate your ovulation date and most fertile days based on your menstrual cycle length and last period date.

What you enter

First Day of Last Period
Average Cycle Length

What you get

Estimated Ovulation Date(primary)
Fertile Window Start
Fertile Window End
Next Period Expected

Use Ovulation Calculator

Key Differences

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

Input Comparison

Only in Due Date Calculator

Calculate Based On
Date
Average Cycle Length (for LMP)

Only in Ovulation Calculator

First Day of Last Period
Average Cycle Length

Which Calculator Should You Use?

Use the Due Date Calculator if you need to:

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

Use the Ovulation Calculator if you need to:

Calculate estimated ovulation date
When you know your first day of last period and average cycle length

Frequently Asked Questions

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.

When do I ovulate?

Ovulation typically occurs 14 days before your next period. For a 28-day cycle, that's day 14. For a 30-day cycle, it's around day 16. Track your cycle for more accuracy.

How long is the fertile window?

The fertile window is about 6 days: the 5 days before ovulation and ovulation day itself. Sperm can survive up to 5 days in the reproductive tract, while the egg is viable for 12-24 hours.

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Bottom Line

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

Use Due Date Calculator Use Ovulation Calculator

Feature

Due Date Calculator

Ovulation Calculator