Pearl Index Calculator
Measure contraceptive failure rate
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The Pearl Index measures how effective a birth control method is in real-world use. It represents the number of unintended pregnancies per 100 women using a method for one year.
The lower the Pearl Index, the more effective the contraceptive method. A Pearl Index of 1 means roughly 1 out of 100 women using the method for a year would become pregnant.
1
Number of Unintended Pregnancies
2
Number of Women in the Study
3
Study Duration
Choose whichever unit matches how your study duration was reported.
✨ Your Pearl Index
Pearl Index
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Calculation
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Effectiveness Rating
< 1
Excellent — highly effective (e.g. IUDs, implants).
1–9
Good — typical of hormonal methods used consistently.
10–25
Fair — typical of barrier or behavioral methods.
> 25
Poor — close to no method at all (85 with no contraception).
Compare to Common Methods (Pearl Index)
"Perfect use" = correct, consistent use every time. "Typical use" = real-world use including missed doses or errors.