Dental practice patient attrition formula — the 3 versions and which to use
Three common formulas — 'lost patients,' 'lapsed,' and 'dormant' — each compute a different number. Pick wrong and your dashboard lies to you.
Why you need a formal formula
Every dental practice-management consultant uses a different 'attrition' number. Some count any patient not seen in 6 months. Some only count patients with no future appointment. Some exclude new patients with <1 completed visit. The three formulas below each have valid use cases; using the wrong one systematically over- or under-reports your leak.
Formula 01 · Lost-patient rate (Levin Group standard)
Formula: (Patients seen in prior 18 months - Patients seen in current 18 months) / Patients seen in prior 18 months × 100
Example: If you saw 2,100 patients in the 18 months ending Dec 2024 and 1,920 in the 18 months ending Dec 2025, your lost-patient rate is (2,100-1,920)/2,100 = 8.6%.
Use case: Year-over-year practice health. Industry benchmark 8-12%.
Formula 02 · Lapse rate (simpler, more common)
Formula: Patients whose last visit is 13+ months old / Total active patient list × 100
Example: 2,000 active patients, 180 haven't been in 13+ months → 9% lapse rate.
Use case: Point-in-time snapshot. Easier to calculate. What most PMS systems and marketing tools use. Slightly understates attrition vs. Formula 01 because it ignores patients who aged out of 'active' entirely.
Formula 03 · Dormant-patient rate (the one everyone uses wrong)
Formula: Patients whose last visit is 24+ months old AND who have NOT been flagged as moved/deceased / Total all-time patient list × 100
Example: Practice has 5,000 all-time patients; 850 are 24+ months with no flag = 17% dormant rate.
Use case: Useful for bulk reactivation campaigns (one-time sweep). NOT a useful year-over-year metric — the denominator grows every year as new patients age in.
Which to use for what
Track quarterly: Formula 01 (Lost-patient rate). Standardizes year-over-year.
Trigger reactivation campaigns: Formula 02 (Lapse rate). Most actionable weekly.
Plan an annual sweep: Formula 03 (Dormant rate). Once per year, go after the whole dormant list in a coordinated 30-day push.
The $77k number for a typical practice
Formula 02 at 9% on a 2,000-patient practice = 180 lapsed patients/year. At a conservative 1.5 future visits × $285/visit, that's $77,000/year of unrealized production walking out. [Calculator with your specific numbers →](/calculator.html)
Frequently asked
What's the 'right' dental patient attrition rate?
Industry range: 6-14%. Below 6% = exceptional retention (rare). Above 14% = urban high-churn market or structural patient-experience problem.
Does insurance churn count as attrition?
Usually yes. If a patient switches insurance and doesn't come back, that's attrition even if their life circumstances are unchanged. Recovering these requires a specific insurance-change-focused outreach.
How often should I recalculate attrition?
Monthly rolling for Formula 01 and 02. Quarterly for Formula 03. Set a dashboard alert if Formula 02 rises >2 percentage points in any quarter.
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