Pregnancy Conception Calculator
Last updated: October 15, 2026
Estimate conception date, gestational age and time remaining from an expected due date and reference date.
Estimated conception date
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- Estimated gestational age: —
- Estimated days remaining: —
- Estimated last menstrual period: —
On this page
Quick summary: Estimate conception date, gestational age and time remaining from an expected due date and reference date.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate conception date, gestational age and time remaining from an expected due date and reference date.
How to use it
Enter Due-date year; Due-date month; Due-date day; Reference year; Reference month; Reference day. Select Calculate to update the results.
How the calculation works
The estimate subtracts 266 days from the due date for conception and 280 days for the last menstrual period, then compares the reference date.
Worked example: starting scenario
| Due-date year | 2026 |
|---|---|
| Due-date month | 12 |
| Due-date day | 1 |
| Reference year | 2026 |
| Reference month | 7 |
| Reference day | 24 |
| Estimated conception date | 2026-03-10 |
|---|---|
| Estimated gestational age | 21 weeks, 3 days |
| Estimated days remaining | 130 days |
| Estimated last menstrual period | 2026-02-24 |
Important limitations
Pregnancy dating is an estimate and can differ based on cycle length, ovulation, ultrasound and clinical assessment. Consult a qualified healthcare professional.