Convert Btu to kilocalories or kilocalories to Btu with International Table and thermochemical unit options for energy conversions.

Choose the unit definitions and enter the energy in BTU.

IT = International Table; th = thermochemical. Changing units converts the entered quantity.

Food Calories use thermochemical kcal. The initial IT choice is for engineering energy conversions.

Assumptions Assumptions
  • Conversions are energy-to-energy only; no power or rate conversions.
  • Joules (J) are used as the base unit: values use standard constants shown below.
  • Supported definitions: Btu (IT) = 1055.05585262 J; Btu (thermochemical) = 1054.350264489 J; kilocalorie (IT) = 4186.8 J; kilocalorie (thermochemical) = 4184 J.
  • “Calorie” on food labels (Cal) equals 1 thermochemical kilocalorie (kcal).
  • Results use up to 6 decimal places; very small or large values use scientific notation.
When to Use This Calculator
  • Converting heating/cooling energy between Btu and food/thermal kilocalories.
  • Comparing appliance energy ratings or fuel heat content across unit systems.
  • Standardizing engineering or nutrition notes without manual lookup tables.
Input Definitions
  • Btu — select International Table (IT) or thermochemical definition.
  • Kilocalories — select IT or thermochemical definition; 1 thermochemical kcal = 1 Cal (food calorie).
  • Conversions — IT: kcal = Btu × 0.251995761; Btu = kcal × 3.968320719. General: kcal = Btu × (J_per_Btu ÷ J_per_kcal).

Btu to Kilocalories Formula

The following formulas convert between Btu and kilocalories using the International Table (IT) definitions; other definitions are noted below.

kcalIT = 0.251995761 BtuIT
BtuIT = 3.968320719 kcalIT
  • Btu (International Table) = 1055.05585262 J
  • Btu (thermochemical) = 1054.350264489 J
  • Kilocalorie (IT) = 4186.8 J
  • Kilocalorie (thermochemical) = 4184 J

How do you convert Btu to kilocalories? For IT units, multiply Btu by 0.251995761; for thermochemical, multiply Btu by (1054.350264489 ÷ 4184) ≈ 0.251996.

How do you convert kilocalories to Btu? For IT units, multiply kilocalories by 3.968320719; for thermochemical, multiply kilocalories by (4184 ÷ 1054.350264489) ≈ 3.968321.

Btu to Kilocalories Conversion Table

Btu (IT) to Kilocalories (IT)
Btu (IT) Kilocalories (IT)
0.50.125998
10.251996
20.503992
30.755987
51.259979
102.519958
153.779936
205.039915
256.299894
307.559873
4010.079830
5012.599788
7518.899682
10025.199576
15037.799364
20050.399152
25062.998940
500125.997881
1000251.995761
* IT definitions: 1 Btu ≈ 0.251996 kcal; 1 kcal = 3.968321 Btu (rounded).

Example Problem

Convert 2,500 Btu (IT) to kilocalories (IT).

Use the IT formula: kcal = Btu × 0.251995761.

kcal = 2,500 × 0.251995761 ≈ 629.989403 ≈ 629.989 kcal