British Thermal Units to Calories Converter
1 British thermal unit ≈ 252.164401 calories
Several BTU definitions exist. This converter uses the International Table BTU, the one used by HVAC equipment ratings.
This is the small calorie. The "Calorie" on food labels is a kilocalorie, which is 1,000 of these.
1 British thermal unit equals 252.164 calories
How to convert British thermal units to calories
Calories here are thermochemical (4.184 J), while BTU uses the International Table definition. A kilowatt-hour is energy (3.6 MJ), not power; a food Calorie is a kilocalorie.
cal = BTU × 252.1644007One British thermal unit is 252.1644007 calories, so a single multiplication converts any value.
2,521.64 cal ≈ 10 × 252.1644007Several BTU definitions exist. This converter uses the International Table BTU, the one used by HVAC equipment ratings.
This is the small calorie. The "Calorie" on food labels is a kilocalorie, which is 1,000 of these.
British thermal units to calories conversion table
Common values in British thermal units, converted to calories.
| British thermal units (BTU) | Calories (cal) |
|---|---|
| 1 | 252.1644 |
| 2 | 504.3288 |
| 3 | 756.4932 |
| 4 | 1,008.6576 |
| 5 | 1,260.822 |
| 10 | 2,521.644 |
| 20 | 5,043.288 |
| 25 | 6,304.11 |
| 50 | 12,608.22 |
| 100 | 25,216.44 |
| 250 | 63,041.1 |
| 500 | 126,082.2 |
| 1,000 | 252,164.4 |
About these units
British thermal unitBTU
The International Table BTU: 1,055.05585262 joules. The US heating and cooling unit.
Reference: NIST Special Publication 811.
caloriecal
The thermochemical calorie: exactly 4.184 joules.
Reference: NIST Special Publication 811.
Sources and precision
Table results are rounded to 8 significant digits; formula constants may be rounded to 10. Worked example answers use 6 significant digits. The converter starts at 6 significant digits and lets you change display precision. Calculations use the stored factors without intermediate rounding. Exact unit definitions do not make an input measurement more precise; conventional and measured factors follow the assumptions stated here.