# Pregnancy Conception Calculator

> Back-calculate an estimated conception date and possible intercourse window from a due date, LMP, ultrasound, conception record, or IVF transfer.

Page: https://askcalculators.com/calculator/pregnancy-conception-calculator/
Definition: https://askcalculators.com/calculator/pregnancy-conception-calculator/definition.json
JSON Schema: https://askcalculators.com/calculator/pregnancy-conception-calculator/schema.json
Version: 2.0.0
Maintained by: AskCalculators (software project; not a credentialed reviewer)
Qualified review: pending. Automated checks do not establish professional approval.
Page status: Live
Review status: Pending

## Use
Open the calculator page and enter values. Query-string parameters can restore and bookmark a calculation.
Example: https://askcalculators.com/calculator/pregnancy-conception-calculator/?method=due&dueDate=2027-03-08

## Inputs
- method: Dating method; type=select; required; default=due; values=due|lmp|conception|ultrasound|ivf
- dueDate: Known due date; type=date; required; default=2027-03-08; showWhen=method:due
- lmpDate: First day of last menstrual period; type=date; required; default=2026-06-01; showWhen=method:lmp
- cycleLength: Average cycle length; type=number; required; default=28; min=20; max=45; showWhen=method:lmp
- conceptionDate: Known conception date; type=date; required; default=2026-06-15; showWhen=method:conception
- ultrasoundDate: Ultrasound date; type=date; required; default=2026-08-24; showWhen=method:ultrasound
- ultrasoundWeeks: Gestational age at ultrasound: weeks; type=number; required; default=12; min=0; max=42; showWhen=method:ultrasound
- ultrasoundDays: Additional days; type=number; required; default=0; min=0; max=6; showWhen=method:ultrasound
- transferDate: Embryo transfer date; type=date; required; default=2026-06-20; showWhen=method:ivf
- embryoAgeDays: Embryo age at transfer; type=select; required; default=5; values=3|5|6; showWhen=method:ivf

## Outputs
- conceptionDateResult: Estimated conception date; format=date; primary
- possibleWindow: Possible intercourse window; format=text
- dueDateResult: Estimated due date; format=date
- lmpDateResult: Estimated LMP date; format=date
- methodResult: Method used; format=text

## Formula
Estimated conception = due date − 266 days; possible intercourse window spans approximately five days before through one day after estimated ovulation/conception.

## Rules
- Empty optional inputs are undefined, not zero.
- Hidden conditional inputs are ignored.
- Do not invent missing required inputs.

Notice: Conception cannot usually be identified to one exact day from calendar dates alone. Clinical and assisted-reproduction records may be more precise.