📊 Total People Component
⚖ Rate vs. Office Baseline
Same Headcount, Other Categories
Full Calculation Table
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How to Use the CFM Per Person Calculator
Choose the space type closest to your zone to load its default Rp value, or pick Other / Custom to enter your own.
Enter the number of people expected in the zone at design occupancy.
Click Calculate to see the total people-based airflow and how the same headcount would compare in other occupancy categories.
Understanding Rp, the People Outdoor Air Rate
Rp is one half of the ASHRAE 62.1 Ventilation Rate Procedure. It sets the outdoor airflow needed per occupant to dilute the odours and other contaminants people give off just by being in a room. This calculator isolates that one number so you can get a quick answer without working through a full zone calculation, and so you can compare how the rate changes across space types. For 18 people in an office, the people component is 90 CFM (45 L/s). The same 18 people in a gym need 360 CFM (180 L/s).
Rp in Canadian Practice
Canadian building codes reference ASHRAE 62.1 for ventilation in non-residential buildings, and Health Canada's guidance on improving indoor air quality in office buildings treats its rates as a minimum. ASHRAE publishes Table 6-1 in both unit systems, and the metric column is rounded: 5 CFM is listed as 2.5 L/s, not the 2.36 L/s a straight conversion gives. Each unit mode here uses the published figure for that system, so totals can differ by a few percent between modes. Provinces adopt specific editions and add amendments, so confirm which one applies before a permit drawing is stamped.
Why Rp Varies by Space Type
Table 6-1 assigns higher rates where occupants are more active. A health club is listed at 20 CFM (10 L/s) per person, four times the 5 CFM (2.5 L/s) for an office, because exertion raises breathing rate and the odour and carbon dioxide each person gives off. Retail, restaurant, bar and mall spaces sit at 7.5 CFM (3.8 L/s), and classrooms and daycares at 10 CFM (5 L/s). The table does not state a separate reason for each value, so treat it as a lookup rather than something to adjust by feel. Carbon dioxide is not what the rate protects against. Health Canada's carbon dioxide guideline describes indoor CO2 as a surrogate for ventilation rate that tracks occupant-generated pollutants and odours, which is why CO2 readings are used to check whether a space is getting enough outdoor air.
Rp Is Only Half the Picture
The people component covers occupants, but most zones also need an area-based component, Ra, that scales with floor area regardless of how many people are in the room. A nearly empty conference room still needs ventilation for off-gassing from furniture and finishes. For the full calculation that adds both components together and applies air distribution effectiveness, use the ASHRAE 62.1 calculator. To test a finished design against the standard, the ASHRAE 62.1 compliance calculator is the next step.
From CFM Per Person to a Real System
Once you know the people-based airflow, it becomes part of the heating and cooling load the system has to handle, especially in a Canadian winter when that outdoor air arrives well below room temperature. Convert this number into a load with the ventilation heat load calculator, and check whether an HRV or ERV could recover some of that energy with the HRV calculator or ERV calculator. The same people also add heat to the room, which the cooling system has to remove. The heat gain from people calculator covers that side of the load.
Variable Occupancy Spaces
Spaces like gyms, restaurants, and conference rooms rarely sit at design occupancy all day. If a space spends most of its time well below the headcount used here, demand-controlled ventilation can reduce outdoor air automatically when fewer people are present. Estimate the potential savings with the demand-controlled ventilation calculator, and check indoor carbon dioxide levels directly with the CO2 calculator.
Frequently Asked Questions
Rp is the people outdoor air rate in ASHRAE 62.1, listed in CFM per person and L/s per person. It is the part of a zone's minimum outdoor air that scales with headcount, and it is set to dilute the odours and other contaminants people give off. Carbon dioxide is not the target. It is used as an indicator of how well those contaminants are being diluted. Table 6-1 gives an Rp for each occupancy category, for example 5 CFM (2.5 L/s) for an office and 20 CFM (10 L/s) for a health club.
CFM per person, or Rp, is only one of two components in the ASHRAE 62.1 Ventilation Rate Procedure. The other is Ra, the area-based rate, which scales with floor area regardless of occupancy. A zone's total breathing zone airflow, Vbz, adds both components together, so CFM per person alone understates the full requirement for most spaces. Use the ASHRAE 62.1 calculator for the complete picture.
Table 6-1 gives higher rates where occupants are more active. A health club is listed at 20 CFM (10 L/s) per person against 5 CFM (2.5 L/s) for an office, because exertion raises breathing rate and the odour and carbon dioxide each person gives off. Retail, restaurant, bar and mall spaces are 7.5 CFM (3.8 L/s), and classrooms and daycares are 10 CFM (5 L/s). The table does not state a separate reason for each value, so treat it as a lookup rather than something to adjust by feel.
Canadian building codes reference ASHRAE 62.1 for ventilation in non-residential buildings, so the same Table 6-1 values apply on both sides of the border, subject to the edition and provincial amendments adopted for a given project. The metric column is published in rounded L/s, so 5 CFM appears as 2.5 L/s, not the 2.36 L/s a straight conversion gives. Always confirm the exact edition adopted in your jurisdiction.