Calculate exactly how many weeks pregnant you are and your estimated due date.
A pregnancy lasts an average of 40 weeks (280 days) from the last period.
Trimester 1: Weeks 1-13. Trimester 2: Weeks 14-27. Trimester 3: Weeks 28-40.
Use this calculator as a starting point for any health or fitness goal that requires a numeric benchmark. The result is an estimate, not a diagnosis — but it provides a concrete figure to track against over time.
The most common mistake is treating the result as a precise measurement rather than an evidence-based estimate. All body metric calculators have margins of error — use the result as a tracking baseline, not a clinical diagnosis.
A personal trainer uses the calculator with a new client to set a measurable starting point. Re-running the calculation at 4-week intervals provides an objective progress metric that supports motivation and programme adjustments.
Count the days since your last menstrual period and divide by 7.
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