Compare calculators
Both calculators run independently β change the inputs on either side to compare results.
Due Date Calculator (Naegele's Rule)
Estimate your due date from your last menstrual period using Naegele's rule, adjusted for your actual cycle length and luteal phase so a non-28-day cycle isn't misdated.
Days until estimated due date
224 days
More than 189 days until your due date puts you in the first trimester (under ~13 weeks), the window covering the dating ultrasound and initial prenatal visit.
Counts calendar days until your estimated due date using Naegele's rule (266 days from conception), so each band corresponds to a pregnancy trimester window.
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 β 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.
Key differences
| Due Date Calculator (Naegele's Rule) | Ovulation & Fertile Window Calculator | |
|---|---|---|
| Category | Pregnancy | Pregnancy |
| Inputs required | 3 | 3 |
| Result | Days until estimated due date (days) | Days until ovulation (days) |
| What it does | Estimate your due date from your last menstrual period using Naegele's rule, adjusted for your actual cycle length and luteal phase so a non-28-day cycle isn't misdated. | Pinpoint your likely ovulation day and fertile window from your cycle length, luteal phase, and the cycle day you're on today β based on the fixed-luteal-phase method. |