kJ to BTU Converter
Convert kilojoules to BTU and BTU to kilojoules, live in both directions. This page uses the International Table BTU: 1 BTU(IT) = 1055.05585262 J exactly, so 1 kJ = 0.9478171203 BTU(IT).
Live converter
Quick conversion tables
Kilojoules to BTU
| kJ | BTU(IT) |
|---|
BTU to kilojoules
| BTU(IT) | kJ |
|---|
Tables use the IT convention at 4 decimals. For exact values, use the converter above with 10-decimal precision.
Which BTU? Convention documented
“BTU” is not one unit. This page uses the IT (International Table) definition everywhere. Others differ by up to ~0.5%:
| Variant | Joules | Notes |
|---|---|---|
| BTU(IT) | 1055.05585262 (exact) | Used here. NIST, EIA, HVAC industry. |
| BTU(th) | 1054.350264488 | Thermochemical. Chemistry legacy. 0.0669% below IT. |
| BTU(mean) | ≈ 1055.87 | Average over 0–100 °C. Rare. |
| BTU(39 °F) | ≈ 1059.67 | Defined at 39 °F water. ≈ 0.44% above IT. |
Cross-convention rule: if your source quotes BTU(th), multiply this page's BTU(IT) result by 0.9993312315.
HVAC and energy-bill context
- 1 kWh = 3,412.1416 BTU(IT) — the bridge between electric bills and heating ratings.
- 12,000 BTU/h = 12,660.6702 kJ/h = 3.51685284 kW — this is 1 ton of refrigeration.
- AC and furnace capacity is a rate (BTU/h); total heat delivered is energy (BTU or kJ).
- BTU to tons of refrigeration converter
Typical appliance ratings (approximate BTU/h)
- Window air conditioner: 5,000–12,000 BTU/h
- Central air conditioner: 18,000–60,000 BTU/h
- Gas furnace: 40,000–120,000 BTU/h
- Gas range burner: 7,000–18,000 BTU/h
- Tank water heater: 30,000–50,000 BTU/h
Ranges are typical manufacturer ratings; actual input varies by model and setting.
Frequently asked questions
What is the formula to convert kJ to BTU?
Multiply kilojoules by 0.9478171203, or equivalently divide by 1.05505585262. E(BTU) = E(kJ) × 0.9478171203 = E(kJ) ÷ 1.05505585262. Both forms use the International Table (IT) definition of the BTU: 1 BTU(IT) = 1055.05585262 J, exact by definition.
How many BTU are in 100 kJ?
100 kJ = 94.7817 BTU (IT). The calculation: 100 × 0.9478171203 = 94.78171203, rounded to 4 decimals. Use the converter above with the precision control to see more digits.
How do you convert BTU to kJ?
Multiply BTU by 1.05505585262. 1 BTU(IT) = 1.05505585262 kJ exactly, since 1 BTU(IT) is defined as 1055.05585262 joules. For example, 500 BTU = 500 × 1.05505585262 = 527.5279 kJ.
Which BTU definition does this converter use: IT or thermochemical?
This converter uses the BTU(IT), the International Table BTU: 1 BTU(IT) = 1055.05585262 J, exact. This is the convention used by NIST, the U.S. Energy Information Administration (EIA), and the HVAC industry, so it matches AC tonnage ratings and energy-bill figures.
What is the difference between BTU(IT) and BTU(th)?
BTU(IT) = 1055.05585262 J (exact, International Table) while BTU(th) = 1054.350264488 J (thermochemical, a chemistry legacy). They differ by about 0.0669%. If your source uses BTU(th), multiply this page's BTU result by 0.9993312315 to convert.
Is the kJ to BTU conversion exact?
Under the IT convention it is exact by definition, because both the kilojoule (1000 J, SI) and the BTU(IT) (1055.05585262 J) are defined values. Real-world measurements of heat are never that precise, so the tiny 0.0669% gap between the IT and thermochemical BTU conventions matters more than decimal places.
How many BTU are in 1 kWh?
1 kWh = 3412.1416 BTU(IT). Derivation: 1 kWh = 3,600,000 J; divide by 1055.05585262 J per BTU = 3412.141633, rounded to 4 decimals. Cross-check: 3600 kJ × 0.9478171203 = 3412.141633 BTU.
How many kJ are in 12,000 BTU, and how many kW is 12,000 BTU/h?
12,000 BTU(IT) = 12,660.6702 kJ of energy. As a power rate, 12,000 BTU/h = 3.51685284 kW (exact under the IT convention: 12,000 × 1055.05585262 ÷ 3600). This is why 1 ton of refrigeration equals about 3.517 kW of cooling capacity.
Why do HVAC systems use BTU instead of kilojoules?
The BTU is the legacy unit of the U.S. heating and cooling industry, where equipment is rated in BTU per hour: a typical window AC is 5,000–12,000 BTU/h, central AC 18,000–60,000 BTU/h, and gas furnaces 40,000–120,000 BTU/h. Metric countries rate the same equipment in kW, which is why this conversion is needed.
How do you convert BTU/h to kW?
Multiply BTU/h by 0.0002930710702. 1 BTU/h = 1055.05585262 J ÷ 3600 s = 0.2930710702 W, so 1000 BTU/h = 0.29307107 kW. This is a power conversion (rate of energy flow), not to be confused with BTU as a total energy amount.
How many kJ are in one therm of natural gas?
1 U.S. therm = 100,000 BTU(IT) = 105,505.5853 kJ (about 105.5 MJ). Gas utilities define the therm as exactly 100,000 BTU, so under the IT convention the kilojoule figure follows by multiplication.
What is the difference between BTU and BTU/h?
BTU measures total energy (like liters in a tank); BTU/h measures power, the rate of energy flow (like liters per minute). A 60,000 BTU/h furnace running for 1 hour delivers 60,000 BTU of heat, which equals 63,303.3512 kJ.
How many BTU are in 1 food Calorie?
1 food Calorie (1 kcal, thermochemical) = 3.96566683 BTU(IT): 4.184 kJ × 0.9478171203 = 3.96566683 BTU. So a 2,000 kcal daily diet represents about 7,931 BTU of chemical energy.
What is a quick mental shortcut for kJ to BTU?
Multiply by 0.95 and subtract roughly 0.24% of the result. For example, 100 kJ × 0.95 = 95, minus 0.24% ≈ 94.78 BTU, very close to the exact 94.7817 BTU. Use the converter above when you need full precision.
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