Air Filter Change Interval Calculator
Estimate how frequently you should replace your HVAC air filter based on filter type, household conditions, and environmental factors.
Formula
Load Factor (LF)
LF = F_size × F_occupant × F_pet × F_smoker × F_allergy × F_dust F_size = homeSize / 2,000 F_occupant = max(0.80, 1 + (occupants − 2) × 0.10) F_pet = 1 + pets × 0.20 F_smoker = 1.50 (smoker present) | 1.00 F_allergy = 0.75 (allergy/asthma) | 1.00 F_dust = 1.30 (dusty/construction) | 1.00
Adjusted Filter Life
adjustedHours = baseHours / LF days = adjustedHours / dailyRuntime days = clamp(days, 7, 365)
baseHours is the manufacturer-rated filter life in operating hours: Fiberglass ≈ 1,500 h · Pleated 1″ ≈ 2,160 h · Pleated 4″ ≈ 4,320 h · High-Efficiency ≈ 8,760 h.