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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

Months and trimester

4.6 months (2nd trimester)

Pregnancy

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)

Days until ovulation

8 days

Ovulation passedPeak fertilityFertile windowPre-fertile phase

More than 6 days until ovulation means you are before the fertile window. Conception is unlikely now; the window opens about 5 days before your predicted ovulation.

Counts days until ovulation as (cycle length minus luteal phase) minus current cycle day; the fertile window spans the 5 days before ovulation through ovulation day itself.

Key differences

	Pregnancy Weeks to Months Converter	Ovulation & Fertile Window Calculator
Category	Pregnancy	Pregnancy
Inputs required	3	3
Result	Months and trimester	Days until ovulation (days)
What it does	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.	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.