Compare calculators
Both calculators run independently β change the inputs on either side to compare results.
Conception Date Estimate Calculator
Estimate how many days ago conception likely occurred from your last menstrual period, corrected for your cycle length and luteal phase rather than assuming day-14 ovulation.
Days since estimated conception
42 days
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.
Key differences
| Conception Date Estimate Calculator | Due Date Calculator (Naegele's Rule) | |
|---|---|---|
| Category | Pregnancy | Pregnancy |
| Inputs required | 3 | 3 |
| Result | Days since estimated conception (days) | Days until estimated due date (days) |
| What it does | Estimate how many days ago conception likely occurred from your last menstrual period, corrected for your cycle length and luteal phase rather than assuming day-14 ovulation. | 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. |