Compare calculators
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.
Days until ovulation
8 days
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.
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.
Months and trimester
4.6 months (2nd trimester)
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. |