CFM Chart: Airflow by Room Size
CFM Quick Reference Chart — Residential Rooms
This chart shows the approximate CFM required for common residential room sizes. Values assume 8-foot ceilings. For higher ceilings, multiply by the correction factor at the bottom of the chart.
| Room Size (sq ft) | Typical Dimensions | Bedroom (1.0 CFM/sqft) | Living Room (1.0 CFM/sqft) | Kitchen (1.5 CFM/sqft) | Bathroom (1.25 CFM/sqft) | Office (1.0 CFM/sqft) |
|---|---|---|---|---|---|---|
| 50 | 5 × 10 | 50 | 50 | 75 | 63 | 50 |
| 75 | 8 × 10 | 75 | 75 | 113 | 94 | 75 |
| 100 | 10 × 10 | 100 | 100 | 150 | 125 | 100 |
| 120 | 10 × 12 | 120 | 120 | 180 | 150 | 120 |
| 144 | 12 × 12 | 144 | 144 | 216 | 180 | 144 |
| 150 | 10 × 15 | 150 | 150 | 225 | 188 | 150 |
| 180 | 12 × 15 | 180 | 180 | 270 | 225 | 180 |
| 200 | 10 × 20 | 200 | 200 | 300 | 250 | 200 |
| 250 | 12 × 20 | 250 | 250 | 375 | 313 | 250 |
| 300 | 15 × 20 | 300 | 300 | 450 | 375 | 300 |
| 400 | 20 × 20 | 400 | 400 | 600 | 500 | 400 |
| 500 | 20 × 25 | 500 | 500 | 750 | 625 | 500 |
| 600 | 20 × 30 | 600 | 600 | 900 | 750 | 600 |
| 800 | 20 × 40 | 800 | 800 | 1,200 | 1,000 | 800 |
| 1,000 | 25 × 40 | 1,000 | 1,000 | 1,500 | 1,250 | 1,000 |
Note: All values assume 8-foot ceilings. For 10-foot ceilings, multiply by 1.25. For 12-foot ceilings, multiply by 1.5.
CFM by Bathroom Size
Bathrooms need dedicated exhaust ventilation. Here is a quick lookup by common bathroom sizes:
| Bathroom Size | Square Feet | Recommended Fan CFM | Fan Size Label |
|---|---|---|---|
| Half bath (powder room) | 20–35 | 50 CFM | Small |
| Small full bath | 35–50 | 50–70 CFM | Small–Medium |
| Standard full bath | 50–80 | 70–100 CFM | Medium |
| Large full bath | 80–120 | 100–150 CFM | Medium–Large |
| Master bath (no tub) | 100–150 | 120–180 CFM | Large |
| Master bath (with tub) | 120–200 | 150–250 CFM | Extra Large |
| Spa bathroom | 150–300 | 200–400 CFM | Extra Large |
For a detailed guide on bathroom ventilation, see our Bathroom Exhaust Fan CFM Guide.
CFM by Kitchen Size
Kitchens require higher CFM due to cooking heat, steam, grease, and odors. The values below assume a standard residential kitchen with a 4-burner stove:
| Kitchen Size | Square Feet | Min CFM (General) | Range Hood CFM* |
|---|---|---|---|
| Small kitchen | 70–100 | 105–150 | 150–300 |
| Medium kitchen | 100–200 | 150–300 | 300–600 |
| Large kitchen | 200–300 | 300–450 | 600–900 |
| Open-plan kitchen/dining | 300–500 | 450–750 | 600–1,200 |
| Commercial kitchen | 500+ | 750+ | 1,000–3,000+ |
*Range hood CFM is typically based on stove width (100 CFM per linear foot for standard residential; higher for commercial or high-BTU cooktops).
CFM by Commercial Space Type
Commercial buildings follow ASHRAE 62.1. Here are common commercial space sizes and their typical CFM requirements:
| Space Type | Typical Size (sq ft) | Estimated CFM | Basis |
|---|---|---|---|
| Private office | 100–150 | 100–200 | 5 CFM/person + 0.06 CFM/sqft |
| Open-plan office (10 people) | 500–800 | 130–180 | 50–75 CFM/person + 0.06 CFM/sqft |
| Conference room (20 people) | 400–600 | 125–160 | 100 CFM/person + 0.06 CFM/sqft |
| Classroom (30 students) | 750–900 | 390–435 | 10 CFM/student + 0.12 CFM/sqft |
| Retail store | 1,000–5,000 | 270–1,350 | 7.5 CFM/person + 0.12 CFM/sqft |
| Restaurant (50 seats) | 1,000–2,000 | 555–1,110 | 7.5 CFM/person + 0.18 CFM/sqft |
Ceiling Height Correction Multiplier
All CFM values in the charts above assume 8-foot ceilings. For other ceiling heights, multiply by the appropriate factor:
| Ceiling Height | Multiply CFM By |
|---|---|
| 7 ft | 0.875 |
| 8 ft (standard) | 1.000 |
| 9 ft | 1.125 |
| 10 ft | 1.250 |
| 12 ft | 1.500 |
| 14 ft | 1.750 |
| 16 ft | 2.000 |
Example: A 300 sq ft living room with 10-ft ceilings: 300 × 1.0 × 1.25 = 375 CFM.
How to Choose the Right Fan or Register
Once you know the required CFM from the chart, choose equipment that meets or slightly exceeds that value:
- Exhaust fans: Match the chart CFM. Fans are rated at 0.1 in. w.g. static pressure — actual delivery drops with duct length and elbows.
- Supply registers: Select a register size that handles the CFM at 50–75 FPM throw velocity for quiet operation.
- Range hoods: For residential, 100 CFM per linear foot of cooktop width. For high-BTU or commercial-style ranges, 150+ CFM per linear foot.
- HVAC supply vents: Use ACCA Manual D for duct sizing and Manual T for register selection to ensure proper air distribution.
Common Mistakes When Reading CFM Charts
- Ignoring ceiling height: A 10-ft ceiling has 25% more volume than an 8-ft ceiling. The CFM must increase accordingly.
- Not accounting for duct losses: Equipment rated at 200 CFM may only deliver 150–180 CFM after friction losses through 30+ feet of duct.
- Undersizing exhaust fans: Bathrooms are the most commonly undersized rooms. Always use the higher CFM range for moisture-prone spaces.
- Oversizing range hoods: An oversized range hood in a tight house can cause backdrafting of combustion appliances. Ensure adequate makeup air.
- Forgetting return air: Supply registers need matching return paths. Without return air, the room pressurizes and supply CFM drops.
Standards and References
- ASHRAE 62.1 — Ventilation for Acceptable Indoor Air Quality (commercial)
- ASHRAE 62.2 — Ventilation and Acceptable Indoor Air Quality in Residential Buildings
- IRC Section M1507 — Residential mechanical ventilation requirements
- ACCA Manual D — Residential Duct Systems
- ACCA Manual T — Air Distribution Basics for Residential and Small Commercial Buildings
Frequently Asked Questions
How do I use the CFM chart?
Find your room size in the left column, then read across to the column matching your room type. The value shown is the approximate CFM required. For example, a 200 sq ft bedroom needs about 150–200 CFM.
What CFM do I need for a 12×12 bedroom?
A 12×12 bedroom (144 sq ft) with a standard 8-foot ceiling needs approximately 108–144 CFM. Use 150 CFM as a practical minimum for a bedroom exhaust fan or supply register.
What CFM do I need for a 10×10 bathroom?
A 10×10 bathroom (100 sq ft) needs approximately 100–150 CFM. For bathrooms with a separate shower enclosure, use the higher end. A 100 CFM exhaust fan is the minimum; 150 CFM is recommended for master bathrooms.
Should I round up or down on the CFM chart?
Always round up to the nearest available fan or register size. It is better to have 10–20% more CFM than needed than to undersize. However, do not oversize by more than 50% as this causes noise and energy waste.
Does the CFM chart apply to all ceiling heights?
The chart values assume standard 8-foot ceilings. For 9-foot ceilings, multiply by 1.125. For 10-foot ceilings, multiply by 1.25. For 12-foot ceilings, multiply by 1.5. Use our CFM calculator for exact results with custom ceiling heights.