Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Ovulation Calculator

Find your estimated ovulation day and 6-day fertile window from how many days ago your last period started, your average cycle length, and your luteal phase. Use it when trying to conceive or to understand your cycle timing.

Days Since Last Period Started (days)

Average Cycle Length (days)

Luteal Phase Length

Number of Cycles to Calculate (cycles)

Fill in the required fields to see your result.

Pregnancy

Due Date Calculator

Estimates how many days remain until your due date and your current pregnancy week from how many days ago your last period (or conception/ultrasound reference) was, plus cycle length and any ultrasound adjustment.

Days Since Last Period (or chosen reference) (days)

Average Cycle Length (days)

Calculation Method

Ultrasound Adjustment (days)

Fill in the required fields to see your result.

Key differences

	Ovulation Calculator	Due Date Calculator
Category	Pregnancy	Pregnancy
Inputs required	4	4
Result	Ovulation & Fertile Window	Due Date Countdown
What it does	Find your estimated ovulation day and 6-day fertile window from how many days ago your last period started, your average cycle length, and your luteal phase. Use it when trying to conceive or to understand your cycle timing.	Estimates how many days remain until your due date and your current pregnancy week from how many days ago your last period (or conception/ultrasound reference) was, plus cycle length and any ultrasound adjustment.