ARCHITECTURE
Ventilation Calculator
Air changes · CFM · Duct sizing · ASHRAE 62.1 · IAQ compliance
CFM
ACH
Occupancy-based ventilation
—
people
m²
m
Required ventilation
—
CFM
Per person rate
—
CFM/person
Per area rate
—
CFM/m²
Total air volume
—
m³
Air changes per hour
—
ACH
Q = (P × Rp) + (A × Ra) | ASHRAE 62.1
Ventilation comparison
Comparison with typical space requirements
Compliance checks
Min ventilation
✓ OK
Per person rate
✓ OK
Per area rate
✓ OK
ACH (min 0.35)
✓ OK
Air changes per hour
m³
CFM
—
ACH
Current ACH
—
ACH
Required airflow
—
CFM
Status
—
—
Space classification
—
—
ACH = (Flow × 60) / Volume | Flow = (ACH × Volume) / 60
ACH gauge
Current ACH vs target
ACH by space type
Typical ACH by space type
Duct sizing
CFM
fpm
—
m
Required area
—
cm²
Duct diameter (round)
—
cm
Rectangular size
—
—
Friction loss
—
in wg/100ft
A = Q / V | D = √(4A/π) | Duct sizing
Duct cross-section
Duct cross-section to scale
Velocity recommendations
Low velocity
200-400 fpm
Residential
Medium velocity
400-800 fpm
Commercial
High velocity
800-1500 fpm
Industrial
Max recommended
2000 fpm
Noise constraint
ASHRAE 62.1 ventilation rates
| Space type | Rp (cfm/person) | Ra (cfm/ft²) | Typical ACH | Notes |
|---|---|---|---|---|
| Office | 5 | 0.06 | 0.5-2.0 | Standard office |
| Classroom | 10 | 0.12 | 0.8-1.5 | Schools, universities |
| Retail | 7.5 | 0.12 | 0.5-1.5 | Stores, shops |
| Restaurant | 7.5 | 0.18 | 1.0-3.0 | Dining areas |
| Residential | N/A | N/A | 0.35-1.0 | Homes, apartments |
| Hospital | N/A | N/A | 2.0-6.0 | Patient rooms |
| Gymnasium | 20 | 0.18 | 1.5-4.0 | Fitness centers |
| Auditorium | 15 | 0.06 | 1.0-2.0 | Assembly spaces |
Rp = per person rate | Ra = per area rate | ASHRAE 62.1-2019