HVAC Unit Conversions and Standards
Tons to BTU/hr, inches of water column to pascals, airflow per ton and SEER versus SEER2, with the worked tables below. No account, nothing to install.
Reference only
These are general industry reference values, not a guarantee for your specific equipment. Always verify against the manufacturer's own specifications. You are responsible for doing your own research before acting on this.
Fixed definitions
- 1 Ton Cooling = 12,000 BTU/hr exactly
- 1 in. W.C. = 248.84 Pa (at 60°F reference basis)
Rules of thumb (approximations)
- Airflow Target: ~400 CFM/ton (typical range 350 - 450 CFM/ton; defers to manufacturer airflow table)
SEER vs SEER2 (DOE M1 Test Procedure)
Effective Jan 2023, SEER2 tests equipment at 0.5" w.g. external static pressure vs 0.1" w.g. for SEER to better reflect real duct systems. SEER2 ratings run roughly 5% lower than SEER for identical equipment.
Tons of cooling to BTU/hr
1 Ton = 12,000 BTU/hr exactly. Each BTU/hr value is the number of tons times 12,000.
| Tons | BTU/hr |
|---|---|
| 0.5 | 6000 |
| 1 | 12000 |
| 1.5 | 18000 |
| 2 | 24000 |
| 2.5 | 30000 |
| 3 | 36000 |
| 3.5 | 42000 |
| 4 | 48000 |
| 4.5 | 54000 |
| 5 | 60000 |
| 5.5 | 66000 |
| 6 | 72000 |
| 6.5 | 78000 |
| 7 | 84000 |
| 7.5 | 90000 |
| 8 | 96000 |
| 8.5 | 102000 |
| 9 | 108000 |
| 9.5 | 114000 |
| 10 | 120000 |
| 10.5 | 126000 |
| 11 | 132000 |
| 11.5 | 138000 |
| 12 | 144000 |
| 12.5 | 150000 |
| 13 | 156000 |
| 13.5 | 162000 |
| 14 | 168000 |
| 14.5 | 174000 |
| 15 | 180000 |
| 15.5 | 186000 |
| 16 | 192000 |
| 16.5 | 198000 |
| 17 | 204000 |
| 17.5 | 210000 |
| 18 | 216000 |
| 18.5 | 222000 |
| 19 | 228000 |
| 19.5 | 234000 |
| 20 | 240000 |
BTU/hr to tons of cooling
Tons are the BTU/hr value divided by 12,000, shown to two decimals.
| BTU/hr | Tons |
|---|---|
| 6000 | 0.50 |
| 12000 | 1.00 |
| 18000 | 1.50 |
| 24000 | 2.00 |
| 30000 | 2.50 |
| 36000 | 3.00 |
| 42000 | 3.50 |
| 48000 | 4.00 |
| 54000 | 4.50 |
| 60000 | 5.00 |
| 66000 | 5.50 |
| 72000 | 6.00 |
| 78000 | 6.50 |
| 84000 | 7.00 |
| 90000 | 7.50 |
| 96000 | 8.00 |
| 102000 | 8.50 |
| 108000 | 9.00 |
| 114000 | 9.50 |
| 120000 | 10.00 |
| 126000 | 10.50 |
| 132000 | 11.00 |
| 138000 | 11.50 |
| 144000 | 12.00 |
| 150000 | 12.50 |
| 156000 | 13.00 |
| 162000 | 13.50 |
| 168000 | 14.00 |
| 174000 | 14.50 |
| 180000 | 15.00 |
| 186000 | 15.50 |
| 192000 | 16.00 |
| 198000 | 16.50 |
| 204000 | 17.00 |
| 210000 | 17.50 |
| 216000 | 18.00 |
| 222000 | 18.50 |
| 228000 | 19.00 |
| 234000 | 19.50 |
| 240000 | 20.00 |
Inches of water column to pascals
1 in. W.C. = 248.84 Pa, so pascals are inches of water column times 248.84.
| in. W.C. | Pa |
|---|---|
| 0.1 | 24.88 |
| 0.25 | 62.21 |
| 0.5 | 124.42 |
| 0.75 | 186.63 |
| 1 | 248.84 |
| 1.5 | 373.26 |
| 2 | 497.68 |
Airflow by tonnage (CFM per ton)
About 400 CFM per ton, typical range 350 to 450 CFM per ton; defers to the manufacturer airflow table.
| Tons | CFM at 350/ton | CFM at 400/ton | CFM at 450/ton |
|---|---|---|---|
| 1.5 | 525 | 600 | 675 |
| 2 | 700 | 800 | 900 |
| 2.5 | 875 | 1000 | 1125 |
| 3 | 1050 | 1200 | 1350 |
| 3.5 | 1225 | 1400 | 1575 |
| 4 | 1400 | 1600 | 1800 |
| 5 | 1750 | 2000 | 2250 |
Frequently asked questions
How many BTU/hr is a ton of cooling?
One ton of cooling is exactly 12,000 BTU/hr. To go from BTU/hr to tons, divide by 12,000; to go from tons to BTU/hr, multiply by 12,000. A 3 ton unit is 36,000 BTU/hr.
How do I convert inches of water column to pascals?
The Equipment Tracker app uses 1 in. W.C. = 248.84 Pa (at 60 degrees F reference basis). Multiply inches of water column by 248.84 to get pascals. The table on this page works it for common static pressure readings.
How much airflow does a ton of cooling need?
The app's rule of thumb is about 400 CFM per ton, with a typical range of 350 to 450 CFM per ton. It is an approximation and defers to the manufacturer's airflow table.
What is the difference between SEER and SEER2?
Effective January 2023, SEER2 tests equipment at 0.5 inch w.g. external static pressure against 0.1 inch w.g. for SEER, to better reflect real duct systems. SEER2 ratings run roughly 5% lower than SEER for identical equipment.
Is there a temperature conversion on this page?
No. The Equipment Tracker app's conversions and standards list covers cooling capacity, static pressure, airflow and SEER, not temperature, so none is shown. For refrigerant temperature against pressure see the refrigerant PT chart.
Does this page store anything or need an account?
No to both. These are general industry reference values, not a guarantee for your specific equipment. Always verify against the manufacturer's own specifications.
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