💊 Contraceptive Failure Rate Simulator

Perfect Use — The Theoretical Ceiling of Contraceptive Efficacy

Perfect use assumes flawless, consistent application every single time.

• 0.3%: Pill (perfect) (failures per year)
• 2%: Condom (perfect) (failures per year)
• 0.2%: IUD (perfect) (failures per year)
• 0.05%: Implant (perfect) (failures per year)

What perfect use means

Perfect use is the clinical trial best case, not everyday life.

Why it rarely reflects reality

Perfect use ignores forgetfulness, timing errors, and misapplication.

Typical Use — How Methods Perform Under Real-World Conditions

Typical use rates capture everyday human inconsistency and error.

• 7%: Pill (typical) (failures per year)
• 13%: Condom (typical) (failures per year)
• 0.2%: IUD (typical) (failures per year)
• 0.05%: Implant (typical) (failures per year)

Sources of typical-use failure

Missed pills, late refills, and incorrect condom application.

Why typical use matters more

Typical use is the number that predicts real pregnancies.

Quantifying the Human Error Factor Across Methods

The gap between perfect and typical use reveals human-factor risk.

• 6.7 pts: Pill gap (typical minus perfect)
• 11 pts: Condom gap (typical minus perfect)
• ~0 pts: IUD gap (typical minus perfect)
• ~0 pts: Implant gap (typical minus perfect)

Why the gap size varies so much

Gap size tracks how much daily behavior the method demands.

Using the gap to counsel patients

A larger gap signals more benefit from adherence support.

LARC Methods — IUD and Implant Remove the Human Factor

Long-acting reversible contraceptives work regardless of daily habits.

• 3–10 yrs: IUD duration (depending on type)
• up to 5 yrs: Implant duration (single insertion)
• none: Consistency needed (after placement)
• yes: Typical ≈ Perfect (near-identical rates)

Why LARC is nearly error-proof

Once placed, there is nothing left for the user to do.

Clinical implications

LARC methods top real-world effectiveness rankings by a wide margin.

Pill and Condom — Effectiveness Tied to Daily Behavior

These methods reward consistency and punish missed or incorrect use.

• 365: Pill actions/year (daily doses required)
• per act: Condom actions (correct use each time)
• high: Consistency effect (drives outcome variance)
• reminders: Support tools (apps, alarms, counseling)

Behavioral demands of these methods

Every dose or act is a fresh chance for error to creep in.

Improving real-world effectiveness

Reminders and habit-stacking can shrink the human error gap.