Indoor Air Quality Score Calculator

Calculate a composite IAQ score (0-100) based on ASHRAE 62.1 ventilation, MERV filtration, CO2, VOC levels, and humidity.

Floor Area (sq ft)

Number of Occupants

Outdoor Air Supply (CFM)

Filter MERV Rating

CO₂ Level (ppm)

Total VOCs (µg/m³)

Relative Humidity (%)

Tab to move between fields

IAQ Score (0-100)

85.4

Ventilation Adequacy (%)182%

CFM per Person20

Required CFM (ASHRAE)220

CO₂ Score (of 20)15

VOC Score (of 15)12.5

RatingExcellent

Well CompliantYes

How to Use This Calculator

Enter Floor Area in sq ft and Number of Occupants for the space.
Enter Outdoor Air Supply in CFM and Filter MERV Rating (MERV 13 is the LEED/WELL standard).
Enter measured CO₂ Level in ppm, Total VOCs in µg/m³, and Relative Humidity percentage.
Review the IAQ Score (0–100) and Ventilation Adequacy percentage vs ASHRAE 62.1 minimum.
Check CFM Per Person and Required CFM to determine if additional outdoor air supply is needed.

How the result changes with CO₂ Level (ppm)

Floor Area (sq ft): Conditioned floor area served by the ventilation system.
Number of Occupants: Typical number of people in the space during occupied hours.
Outdoor Air Supply (CFM): Total outdoor air delivered by the HVAC system in cubic feet per minute.
Filter MERV Rating: MERV rating of air filters. MERV 8 = basic, MERV 13 = LEED/WELL standard, MERV 16+ = hospital grade.
CO₂ Level (ppm): Measured indoor CO₂ concentration. Outdoor ambient ~420 ppm. ASHRAE target: < 1000 ppm indoors.
Total VOCs (µg/m³): Total volatile organic compounds concentration. WELL target: < 500 µg/m³. New buildings often 200-1000.
Relative Humidity (%): Indoor relative humidity. ASHRAE ideal range: 40-60% RH.

IAQ Score (0-100): Composite indoor air quality score. 85+ Excellent, 70-84 Good, 55-69 Acceptable, 40-54 Marginal, <40 Poor.
Ventilation Adequacy (%): Outdoor air delivery as percentage of ASHRAE 62.1 minimum. 100% = meets minimum.
CFM per Person: Outdoor air delivered per occupant. ASHRAE 62.1 office minimum: ~17 CFM/person.
Required CFM (ASHRAE): Minimum outdoor air required per ASHRAE 62.1 for this space and occupancy.
CO₂ Score (of 20): Points earned for CO₂ concentration (max 20).
VOC Score (of 15): Points earned for VOC concentration (max 15).

Identify Input Parameters
4 parameters
Floor Area (sq ft) = 2000, Number of Occupants = 20, Outdoor Air Supply (CFM) = 400, Filter MERV Rating = 13 = 7 input(s) provided
Calculate IAQ Score
IAQ Score = round((ventScore + filtScore + co2Score + vocScore + humScore + sourceScore) ...
85.4 = 85.4
Calculate Ventilation Adequacy
Ventilation Adequacy = outdoorAirCfm / max(1, requiredCfm)
182 = 182%
Calculate CFM per Person
CFM per Person = outdoorAirCfm / occupants
20 = 20