Home Infestation Severity Score Calculator
Estimate the severity of a pest infestation in your home using a weighted scoring model based on pest type, percentage of home affected, duration of infestation, and level of visible damage.
Formula
Severity Score (S) = min( Wp × [0.30×Anorm + 0.25×Dnorm + 0.25×Vnorm + 0.10×Onorm + 0.10×Tnorm] × 100 / 3.0 , 100 )
- Wp — Pest type risk multiplier: Low-risk pests = 1.0; Moderate = 1.5; High = 2.0; Structural = 2.5; Critical/Multiple = 3.0
- Anorm = Area affected (%) / 100
- Dnorm = min(Duration in weeks, 52) / 52 — capped at 1 year
- Vnorm = Visible damage level (0–3) / 3
- Onorm = min(Occupants, 10) / 10 — capped at 10
- Tnorm = Previous treatment score (0–3) / 3
- Division by 3.0 normalizes the maximum possible raw score (Wp,max=3.0) to 100.
Severity Bands: 0–20 Minimal | 21–40 Low | 41–60 Moderate | 61–80 High | 81–100 Critical
Assumptions & References
- The scoring model is a weighted multi-factor index adapted from pest risk assessment frameworks used by pest management professionals (National Pest Management Association, NPMA).
- Pest type multipliers reflect relative public health and structural risk ratings as documented by the EPA and NPMA Pest Library.
- Duration is capped at 52 weeks (1 year) because infestations persisting beyond one year are treated as fully established regardless of exact duration.
- Occupant count is capped at 10 for normalization; larger households increase exposure risk but the marginal effect diminishes beyond 10 people.
- Weights (30% area, 25% duration, 25% damage, 10% occupants, 10% treatment history) reflect expert consensus that spatial spread and persistence are the primary severity drivers.
- This calculator provides an indicative score only and does not replace a professional pest inspection. Always consult a licensed pest control operator for treatment decisions.
- References: EPA Pest Control Guidance (epa.gov); NPMA Pest Library (pestworld.org); WHO Vector Control Guidelines.