Trimester Calculator
Map gestational age to a clearly stated trimester convention and show weeks and days.
Enter or adjust the values above, then calculate.
Trimester: first, Second or Third Trimester
Map gestational age to a clearly stated trimester convention and show weeks and days.
Inputs this tool uses
- Gestational weeks
- Additional days
What you get
Trimester from entered gestational age.
How to use the Trimester Calculator
- Enter gestational weeks, additional days.
- Select any method, activity level or option shown on this page, then choose Calculate.
- Read the main result together with the supporting values, method, assumptions and limitations below before using the estimate.
How this calculation works
Pregnancy dating uses standard LMP, conception or IVF date conventions. Clinical ultrasound and clinician assessment can revise a working due date.
Example calculation
The sample values loaded into the calculator produce Second trimester. This example exists to show how the output is structured; replace the sample values with your own inputs for your calculation.
Assumptions and limitations
- Pregnancy dating is an estimate and clinical ultrasound may change the working due date.
- This tool is educational and does not replace prenatal care or medical advice.
Sources and review status
Source set last verified 2026-09-25. No clinician review is claimed unless a real named reviewer is displayed.
Connected tools
Continue with the closest related calculation without re-entering sensitive values automatically.
Calculate gestational age, trimester, estimated due date, progress and countdown from LMP or due date using date-only arithmetic.
Open tool →◔Due Date CalculatorEstimate due date from LMP, cycle length, conception or IVF-related timing and explain the ultrasound-dating caveat.
Open tool →◔Pregnancy Week CalculatorCalculate current pregnancy week and day from LMP or due date and show the estimated due date.
Open tool →