Calculate birth date and gestation age in 1 pages
Choose to calculate from LMP or the day of conception and see the result as due date + current gestation age.
The results are estimates for preliminary planning.
Birth Date Calculator
The Birth Date Calculator estimates a health and body estimate for your scenario from the quantities, rates, period, units and other assumptions requested on the page. Replace the example values with your own birth date figures and recalculate after changing an assumption. Treat it as a planning estimate and independently verify the current rule or provider terms.
Use this tool to estimate the due date of delivery from the first day of last menstruation (LMP) or from the day of conception, then the system will show the approximate current pregnancy age, helping to plan pregnancy and track development systematically.
Trust information
Use reference information from Thai official agencies. and display results to help plan before making decisions
Last updated: 19 Apr. 2026
source
- NHS Due Date Calculator Guidance
- Johns Hopkins Medicine: Calculating a Due Date
- CDC/NCHS Facility Worksheet Guide (EDD/LMP guidance)
Assumptions and things to note
- It's for preliminary assessment, not medical diagnosis.
- Actual date of delivery may change based on ultrasound results and medical assessment.
Calculation results
Continue: Read how to calculate pregnancy and prepare a spending plan.
After you get your scheduled date, follow up with the pregnancy counting guide and the related numerical planning tool.
The formula used in this calculator
- LMP case: due date = LMP + 280 days (40 weeks)
- Monthly adjustment: EDD = LMP + 280 + (monthly - 28) days
- In case of knowing the conception date: due date = conception day + 266 day
- Current gestation age = today - date of conception (LMP or LMP-equivalent)
Referenced standard formula from NHS and Johns Hopkins Medicine (LMP + 280 days / IVF + 266 days)
This tool is for preliminary planning only. Pregnancy monitoring should be under the supervision of medical personnel, especially in cases of irregular menstruation, pregnancy from assisted reproductive technology or complications.
Official reference source
- Ministry of Health (anamai. moph. go. th) — Health criteria and indicators for Thais
- Ministry of Health (moph. go. th) — National Health Policy and Information
Learn more from our article.
Frequently asked questions
How do you calculate the birth date from the first day of your period?
If I know the day of the resurrection, do I have to calculate differently?
Does the calculation match the date the doctor always gives?
Can you calculate the pregnancy period to the day?
English calculator guide
How to use the Birth Date Calculator
Use this page to test a specific birth date scenario. Enter your own values in the calculator above, review the units beside each field, and recalculate after changing an assumption. The result updates the birth date estimate instead of relying on a generic example.
- Build a baseline birth date case with figures that match your situation.
- Run a second birth date case after changing the rate, period, quantity or other key assumption.
- Record the difference between the two birth date results and the input responsible for it.
Inputs for the birth date estimate
For this birth date calculation, check the quantities, rates, period, units and other assumptions requested on the page. The result is designed to show a health and body estimate for your scenario, not a guaranteed provider price or official decision.
How the birth date result is calculated
The calculator applies the page-specific measurement relationship to the personal values you enter. Reusing the same birth date inputs will produce the same estimate, which makes the page suitable for controlled scenario comparisons.
Checks for a birth date decision
Confirm any current rate, threshold or provider rule that could change the final amount. For birth date, This result is for personal tracking and general education. It is not a diagnosis or treatment recommendation; discuss unusual or concerning results with a qualified health professional. Because this calculation can affect an important financial, legal or health decision, independently verify the inputs and current rules before relying on the result.
- Language QA
- Terminology, numeric values and calculator controls checked
- Calculator scope
- Health and body
- Last English review
- 26 July 2026