Convert cooling tonnage to airflow rate for HVAC system sizing. Quick answer: 1 TR ≈ 400 CFM at the standard 20°F temperature differential — use the calculator below for exact values at any ΔT, or the chart further down for common sizes.
Enter TR value and click Calculate
A Ton of Refrigeration (TR) is a unit of cooling capacity equal to 12,000 BTU/hr. Historically, it represents the heat absorption rate needed to melt one ton (2000 lbs) of ice at 32°F in 24 hours. This unit is widely used in North America and the Middle East for sizing air conditioning systems.
The relationship between cooling capacity and airflow is governed by the sensible heat equation:
CFM = (TR × 12,000) / (1.08 × ΔT)
Where: 1.08 = 0.24 (specific heat of air) × 60 (min/hr) × 0.075 (air density lb/ft³)
For a standard temperature differential of 20°F (typical for comfort cooling), the formula simplifies to approximately 400 CFM per TR. This quick rule is widely used for preliminary HVAC calculations and equipment selection.
| Application | ΔT (°F) | CFM/TR |
|---|---|---|
| Standard Comfort Cooling | 18-22°F | 350-420 |
| High Sensible Load | 15-18°F | 420-500 |
| High Latent Load | 22-28°F | 280-350 |
| Data Centers | 15-20°F | 400-500 |
AHU Sizing: Use this calculator to determine required airflow for Air Handling Units based on cooling coil capacity.
Duct Sizing: Once CFM is known, proceed to size supply and return ducts using appropriate velocity limits.
Diffuser Selection: Total CFM divided by number of zones helps determine diffuser sizes and quantities.
Quick reference for common AC and AHU sizes — CFM at the standard 400 CFM/ton rule, with BTU/hr and metric airflow equivalents:
| TR (Tons) | CFM | BTU/hr | L/s | m³/hr |
|---|---|---|---|---|
| 1 | 400 | 12,000 | 189 | 680 |
| 1.5 | 600 | 18,000 | 283 | 1,019 |
| 2 | 800 | 24,000 | 378 | 1,359 |
| 2.5 | 1,000 | 30,000 | 472 | 1,699 |
| 3 | 1,200 | 36,000 | 566 | 2,039 |
| 4 | 1,600 | 48,000 | 755 | 2,718 |
| 5 | 2,000 | 60,000 | 944 | 3,398 |
| 7.5 | 3,000 | 90,000 | 1,416 | 5,097 |
| 10 | 4,000 | 120,000 | 1,888 | 6,796 |
| 15 | 6,000 | 180,000 | 2,831 | 10,193 |
| 20 | 8,000 | 240,000 | 3,775 | 13,591 |
| 25 | 10,000 | 300,000 | 4,719 | 16,988 |
| 30 | 12,000 | 360,000 | 5,663 | 20,386 |
| 40 | 16,000 | 480,000 | 7,550 | 27,182 |
| 50 | 20,000 | 600,000 | 9,438 | 33,977 |
| 100 | 40,000 | 1,200,000 | 18,876 | 67,954 |
To convert airflow back to cooling tonnage, use:
TR = (CFM × 1.08 × ΔT) / 12,000 or simply TR ≈ CFM ÷ 400
| CFM | TR (Tons) | BTU/hr | kW |
|---|---|---|---|
| 400 | 1 | 12,000 | 3.5 |
| 800 | 2 | 24,000 | 7.0 |
| 1,200 | 3 | 36,000 | 10.6 |
| 2,000 | 5 | 60,000 | 17.6 |
| 4,000 | 10 | 120,000 | 35.2 |
| 6,000 | 15 | 180,000 | 52.8 |
| 8,000 | 20 | 240,000 | 70.3 |
| 10,000 | 25 | 300,000 | 87.9 |
| 20,000 | 50 | 600,000 | 175.9 |
Both charts assume the standard 20°F ΔT — for high sensible or high latent applications, use the calculator above with your actual design ΔT.