Calculate gestational age and estimated due date (EDD) from LMP, Ultrasound, or IVF (D3/D5).
Result
GA today
—
EDD
—
Trimester
—
Total days of gestation—
Completed weeks—
Days remaining until EDD—
Estimated conception date—
Informational tool. Always follow the guidance of your healthcare team.
The gestational calculator estimates the gestational age (GA) in weeks + days and the estimated due date (EDD) from different clinical references: LMP (last menstrual period), Ultrasound, known EDD, or IVF (D3/D5 transfer). Calculations are performed locally in your browser, preserving your privacy.
The tool also displays the trimester, days of gestation, completed weeks, remaining days until EDD, and the estimated conception date (obstetric standard). Results are informational and should be validated by your healthcare team.
How to use the app (step-by-step)
Choose the method: select LMP, Ultrasound, EDD, or IVF (D3/D5) from the selector.
Fill in the fields: enter the date(s); for Ultrasound, include the measured GA (weeks and days); for LMP, adjust the cycle length (e.g., 28d).
Calculate: click Calculate to see today's GA, EDD, trimester, and period details.
Review: open the displayed details and confirm they are consistent with your history and exams.
Clear: use Clear to reset the fields and perform a new calculation.
Application Features (highlights)
Four clinical methods: LMP, Ultrasound, known EDD, and IVF (D3/D5).
Menstrual cycle adjustment: for LMP, consider cycles of 20–45 days to improve the estimate.
Ultrasound with measured GA: enter weeks and days for more accurate dating (especially 1st trimester).
IVF with D3/D5: specific constants to estimate the EDD according to the embryonic stage.
Complete results: GA today, EDD, trimester, days of gestation, completed weeks, remaining days, and estimated conception date.
Privacy by default: all data and calculations remain in your browser.
Accessible and responsive: comfortable use on desktop and mobile, with feedback via aria-live.
Understanding the results and metrics
GA today (wks + days): gestational age on the current date, derived from the chosen method.
EDD: estimate for 40 weeks (280 days) from the provided reference.
Trimester: approximate classification: 1st, 2nd, or 3rd according to the GA in days.
Days of gestation: total elapsed time since the obstetric reference point.
Completed weeks: number of full weeks already completed.
LMP: 280 days are added to the 1st day of the last menstrual period. Cycles ≠ 28d receive a proportional adjustment.
Ultrasound: with the exam date and measured GA, the EDD is projected to 40 weeks. 1st-trimester ultrasound tends to be the most accurate.
Known EDD: when the EDD has already been clinically defined, the tool derives today's GA.
IVF (D3/D5): uses the transfer date as a reference; common constants: D3 ≈ +263d and D5 ≈ +261d to the EDD.
Best Practices
Prefer early ultrasound: when available, the 1st-trimester ultrasound usually guides the final EDD.
Consider cycle irregularities: for very irregular cycles, validate with an imaging exam.
Document the criteria: when sharing results, state the method (LMP/Ultrasound/EDD/IVF) and parameters used.
Multiple gestation: may follow specific recommendations—discuss with your healthcare team.
Common Errors to Avoid
Incorrect dates: entering day/month inverted or selecting the wrong year.
Invalid ultrasound GA: weeks outside 0–45 or days outside 0–6.
Cycle out of range: entering a duration less than 20 or greater than 45 days without guidance.
Comparing methods without context: discrepancies between LMP and ultrasound should be clinically evaluated.
When to revise the estimate?
If a 1st-trimester ultrasound indicates a significant discrepancy compared to the LMP, common practice is to revise the EDD based on the early ultrasound and maintain this reference in subsequent follow-ups.
Frequently Asked Questions (FAQ)
Which method is the most accurate? In general, the 1st-trimester ultrasound provides the highest accuracy for dating the pregnancy.
My cycle is not 28 days. What now? For LMP, the calculator adjusts the estimate according to the provided cycle length.
Why is the GA greater than the time since conception? By convention, the count starts from the LMP (≈ 2 weeks before conception).
Can I use it offline? Yes. After loading the page, the tool works locally in your browser.
Is my data sent anywhere? No. Everything is processed locally; nothing is sent to servers.
Summary
The gestational calculator integrates clinical methods (LMP, Ultrasound, EDD, and IVF) to transparently estimate GA and EDD. Use it as a support tool, document the criteria applied, and validate with your healthcare team—it's practical, private, and informative.
Note: educational content; does not substitute for medical advice, diagnosis, or treatment. Seek your healthcare team for individualized assessment.