BTU to Tons Converter
Convert BTU/hr (British Thermal Units per hour) to tons of refrigeration and kilowatts. Essential for HVAC, air conditioning, and cooling system sizing and comparisons.
1 ton = 12,000 BTU/hr = 3.517 kW
What is a BTU and a Ton of Refrigeration?
A ton of refrigeration (TR) is a unit of power describing the heat absorption capacity of an air conditioning or refrigeration system. One ton of refrigeration equals 12,000 BTU/hr, the amount of heat energy needed to melt 1 short ton (2,000 pounds) of ice at 32°F in 24 hours.
This unit originated from the early days of refrigeration when large ice-production facilities defined cooling capacity by how much ice they could produce. Today, it's still widely used in North America for HVAC systems, but kilowatts (kW) and BTU/hr are also common.
Understanding TR helps when sizing air conditioning units, comparing system efficiency, and interpreting manufacturer specifications. For example, a "2-ton AC unit" absorbs 24,000 BTU/hr of heat from indoor air.
How to convert BTU to tons and kW
Conversion factors follow NIST Special Publication 811. See Sources.
BTU to Tons
To convert BTU/hr to tons of refrigeration, divide by 12,000:
Example: 36,000 BTU/hr = 36,000 ÷ 12,000 = 3 Tons
BTU to kW
To convert BTU/hr to kilowatts, divide by 3412.142:
Example: 36,000 BTU/hr = 36,000 ÷ 3412.142 = 10.55 kW
Tons to kW
One ton of refrigeration is 3.517 kW of cooling, so multiply tons by 3.517:
Example: 2.5 Tons = 2.5 × 3.517 = 8.79 kW
How to convert 48,000 BTU to tons
Sizing an Air Conditioning Unit
Note that 14 kW is the cooling capacity, not the electricity the unit draws. Actual electrical power consumption depends on the unit's efficiency (SEER/EER rating): dividing cooling capacity by EER gives input power, so a 4-ton (48,000 BTU/hr) unit with a typical EER of 10-13 draws roughly 3.7-4.8 kW of electricity, a fraction of its cooling output. You'll still need adequate electrical service (typically 240V) and proper circuit breaker sizing for the compressor unit.
BTU to Tons Conversion Table
Common BTU/hr ratings from window units to light commercial systems. Tons are rounded to 3 decimal places and kW to 2.
| BTU/hr | Tons | kW |
|---|---|---|
| 5,000 | 0.417 | 1.47 |
| 6,000 | 0.5 | 1.76 |
| 8,000 | 0.667 | 2.34 |
| 9,000 | 0.75 | 2.64 |
| 10,000 | 0.833 | 2.93 |
| 12,000 | 1 | 3.52 |
| 15,000 | 1.25 | 4.4 |
| 18,000 | 1.5 | 5.28 |
| 24,000 | 2 | 7.03 |
| 30,000 | 2.5 | 8.79 |
| 36,000 | 3 | 10.55 |
| 42,000 | 3.5 | 12.31 |
| 48,000 | 4 | 14.07 |
| 60,000 | 5 | 17.58 |
| 120,000 | 10 | 35.17 |
| 240,000 | 20 | 70.34 |
Typical Air Conditioner Sizes in BTU and Tons
Typical capacity ranges by equipment type. Use them to sanity-check a quote or spec sheet, not to size a system.
| Equipment | BTU/hr | Tons |
|---|---|---|
| Small window unit (one room) | 5,000–8,000 | 0.4–0.7 |
| Large window or portable unit | 10,000–15,000 | 0.8–1.25 |
| Ductless mini-split (per head) | 9,000–24,000 | 0.75–2 |
| Central AC, small house | 24,000–36,000 | 2–3 |
| Central AC, large house | 48,000–60,000 | 4–5 |
| Light commercial rooftop unit | 120,000+ | 10+ |
Common BTU and Ton Conversion Mistakes
- Dropping the "/hr". A "12,000 BTU air conditioner" means 12,000 BTU per hour. That's a rate (power), and it's what converts to tons. A plain BTU figure is a quantity of energy and has no ton equivalent unless you know the time period.
- Reading cooling kW as electrical kW. A 3-ton unit moves about 10.5 kW of heat but draws much less electricity, about 2.8–3.6 kW at a typical EER of 10–13. Check the nameplate input power or EER for the electrical load.
- Treating the nominal size as exact. Residential units are sold in nominal half-ton steps, so a "3-ton" model is a size class. Actual capacity is rated at standard test conditions, and it drops as outdoor temperature rises. Check the rated BTU/hr on the spec sheet.
- Sizing from square footage alone. Rules of thumb like 20–30 BTU/hr per square foot ignore insulation, windows, orientation and climate. In the US, residential cooling loads are properly calculated with ACCA Manual J.
Frequently Asked Questions
Why is it called a "ton" if it's about heat, not weight?
The term originated from ice production. A "ton" referred to the amount of ice produced (1 short ton = 2,000 lbs). The heat required to melt that ice in 24 hours became the standard unit of cooling capacity, even though it's really a unit of power, not weight.
What's the difference between BTU/hr and BTU?
BTU is a unit of energy (total heat). BTU/hr is power (rate of heat transfer per hour). For cooling systems, we care about BTU/hr - how fast the system removes heat. A 12,000 BTU/hr system removes heat at that rate continuously.
Why do we need kilowatts if we have BTU?
In countries using the metric system and for electrical engineering, kilowatts are the standard. BTU is North American. Both measure power: 1 kW ≈ 3,412 BTU/hr. Using both lets engineers and customers communicate effectively worldwide.
How do I know what size AC unit I need?
A general rule: 20–30 BTU/hr per square foot. A 2,000 sq ft home typically needs 40,000–60,000 BTU/hr (3.3–5 Tons). Hot climates may need more; mild climates may need less. Your HVAC technician considers climate, insulation, and ductwork for exact sizing.
What does SEER or EER mean?
SEER (Seasonal Energy Efficiency Ratio) and EER (Energy Efficiency Ratio) measure how efficiently an AC unit operates. Higher = better. A 4-ton system with SEER 16 uses electricity more efficiently than one with SEER 10, even though both have the same cooling capacity.
Is a bigger AC unit always better?
No. Oversized units short-cycle (turn on/off frequently), wasting energy and not dehumidifying properly. Undersized units run constantly without reaching target temperature. Proper sizing requires matching capacity to actual cooling load.
What's the relationship between BTU and kW?
1 kW = 3,412.142 BTU/hr (precise), or 1 BTU/hr = 0.000293071 kW. This ratio is fixed, perfect for precise conversions. It comes from the definition of BTU relative to the joule (SI unit of energy).
Can I use this only for air conditioning?
No. This conversion applies to any refrigeration or heat removal system: portable ACs, heat pumps, refrigerators, freezers, industrial chillers, etc. Any system with a BTU/hr or ton cooling rating can be converted using these relationships.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units (SI): 1 BtuIT/h = 0.2930711 W; 1 ton of refrigeration (12,000 BtuIT/h) = 3.516853 kW.
- ACCA Manual J, Residential Load Calculation: the US standard method for sizing residential cooling equipment.
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