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

Ovulation & Fertile Window Calculator

Pinpoint your likely ovulation day and fertile window from your cycle length, luteal phase, and the cycle day you're on today — based on the fixed-luteal-phase method.

Current cycle day (day 1 = first day of period) (day)

Average menstrual cycle length (days)

Luteal phase length (days)

Pregnancy

Pregnancy Weeks to Months Converter

Convert pregnancy weeks and days into months and identify your trimester, using either calendar months or four-week 'lunar' months — the two conventions that cause confusion.

Completed weeks of pregnancy (weeks)

Additional days (days)

Month convention

Key differences

	Ovulation & Fertile Window Calculator	Pregnancy Weeks to Months Converter
Category	Pregnancy	Pregnancy
Inputs required	3	3
Result	Days until ovulation (days)	Months and trimester
What it does	Pinpoint your likely ovulation day and fertile window from your cycle length, luteal phase, and the cycle day you're on today — based on the fixed-luteal-phase method.	Convert pregnancy weeks and days into months and identify your trimester, using either calendar months or four-week 'lunar' months — the two conventions that cause confusion.