How to use the pregnancy gestation calculator
Estimate weeks pregnant and days to due date (Naegele rule). Enter days since last period in the field above; the gestational age, days until due date (280 days), trimester are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- d — Days since last period
Worked example
With days since last period = 98, the calculator gives gestational age ≈ 14 weeks; days until due date (280 days) ≈ 182; trimester ≈ 2.
Frequently asked questions
What is the formula for the pregnancy gestation calculation?
Gestational age (weeks) = d / 7. Days until due date (280 days) = 280-d. Trimester = d<91?1:(d<189?2:3). Here d is days since last period.
What inputs do I need for the pregnancy gestation calculator?
You need days since last period. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.