Unit Converter — Free Online Calculator
Nameplates, gauge faces, and manufacturer charts do not always use the same units — tons vs BTU/h, °F vs °C, in. w.c. vs Pa. This three-mode converter handles the conversions HVAC techs reach for on every service call: cooling capacity, air and line temperature, and duct or refrigerant pressure. Pick a mode, enter a value, and get every related unit instantly.
Enter value to convert
Enter the number in the unit selected below.
1 ton = 12,000 BTU/h · kW = BTU/h ÷ 3,412
For setpoints, line temps, and saturation checks.
in. w.c. for duct static; PSI/kPa for refrigerant gauges.
Primary result
Secondary
36,000 BTU/h
Tertiary
10.6 kW
What this means
Capacity conversion — 1 ton = 12,000 BTU/h = 3.517 kW at standard conditions.
See the breakdown
Each mode converts independently — capacity, temperature, and pressure do not cross-multiply. Use manufacturer charts for refrigerant-specific saturation temps and charge targets.
Common capacity conversions (tons · BTU/h · kW)
Standard HVAC capacity equivalents. kW = BTU/h ÷ 3,412 (rounded to one decimal).
| Tons | BTU/h | kW |
|---|---|---|
| 1.5 | 18,000 | 5.3 |
| 2 | 24,000 | 7.0 |
| 3 | 36,000 | 10.6 |
| 4 | 48,000 | 14.1 |
| 5 | 60,000 | 17.6 |
Sources & standards: ASHRAE / IAPWS unit definitions · ACCA Manual D (static pressure units) · AHRI rating conditions for capacity (12,000 BTU/h per ton).
The formulas, explained in plain English
Three independent converters share one input box. Pick the mode that matches what is on your gauge, nameplate, or chart — the tool applies the standard HVAC conversion for that quantity only.
Tons and BTU/h
Equipment nameplates often show BTU in the model number (036 = 36,000 BTU = 3 tons). Converting quickly prevents ordering the wrong capacity or mismatching a coil to a condenser.
kW for specs and customers
Heat pumps and mini-splits sometimes list kW on import specs. Divide BTU/h by 3,412 to compare apples-to-apples with tonnage-rated US equipment.
°F and °C on line temps
Superheat, subcooling, and saturation tables may use either scale. Convert before comparing a clamp reading to a chart — a 5°F error is enough to misdiagnose charge.
Air-side vs refrigerant-side pressure
Duct static pressure uses in. w.c. or Pa; manifold gauges read PSI or kPa. Keep the modes separate — TESP in PSI is not a field reading you will see on a residential job.
Worked examples
Three field conversions techs use every week — capacity from a nameplate, a dry-bulb temp for a metric chart, and duct static pressure in SI units.
3 tons → BTU/h and kW
kW = 36,000 ÷ 3,412 = 10.6 kW
Result: a 3-ton condenser matched to a 36,000 BTU/h coil — the default in this calculator. Model number 036 on the data plate confirms the same capacity.
75°F → Celsius
Result: typical summer return-air dry-bulb — switch to Temperature mode, enter 75 with °F selected, and read 24°C for a metric superheat chart or customer-facing report.
0.5 in. w.c. → Pascals
PSI ≈ 0.018 · kPa ≈ 0.12
Result: a common residential TESP ceiling — 0.5 in. w.c. is the max on many air handlers. Switch to Pressure mode to express the same reading in Pa for a spec sheet or compare with the Static Pressure Calculator.
Frequently asked questions
Common questions about tons, BTU/h, temperature, and pressure conversions in HVAC work.
How many BTU is 3 tons of cooling?
Three tons equals 36,000 BTU/h. One ton of refrigeration is defined as 12,000 BTU/h — the heat needed to melt one short ton of ice in 24 hours. Multiply any tonnage by 12,000 to get BTU/h, or divide BTU/h by 12,000 to get tons.
How do I convert HVAC tons to kW?
First convert tons to BTU/h (tons × 12,000), then divide by 3,412 to get kilowatts. A 3-ton system is 36,000 BTU/h, which equals about 10.6 kW of cooling capacity at standard rating conditions.
What is in. w.c. in HVAC ductwork?
Inches of water column (in. w.c.) is the standard unit for measuring total external static pressure (TESP) on residential and light-commercial duct systems. Manometers and digital gauges on the air side typically read in. w.c.; manufacturer limits are usually 0.5–0.8 in. w.c. for residential equipment.
How do I convert °F to °C for line temperatures?
Use °C = (°F − 32) × 5/9. For example, 75°F dry-bulb is 24°C. Reverse it with °F = (°C × 9/5) + 32. Field thermometers and manufacturer charts may use either scale — convert before comparing to a charging chart or superheat table.
When do I use PSI vs kPa on refrigerant gauges?
Refrigerant manifold gauges in the US typically read PSI; metric charts and European equipment often use kPa. Convert with kPa = PSI × 6.895. Static pressure on the air side uses in. w.c. or Pa — do not mix air-side and refrigerant-side units on the same reading.
Why is one ton equal to 12,000 BTU/h?
The ton dates to ice-storage cooling: one ton of refrigeration removes heat at the rate needed to melt 2,000 lb of ice in 24 hours, which works out to 12,000 BTU/h. Modern equipment is still rated in tons and BTU/h even though ice-based cooling is obsolete.
When do HVAC techs need a unit converter in the field?
Any time specs cross unit systems: matching a 36,000 BTU nameplate to 3 tons, comparing a 0.5 in. w.c. duct reading to a 125 Pa spec, converting a 95°F saturation temp for a metric PT chart, or quoting kW for a customer who thinks in tons. This tool covers the three conversions that come up most on service calls.
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