Choose Btu from calories or Calories from Btu, then enter the energy value and select the source and result standards. Food Calories use thermochemical kilocalories (kcal). Signed inputs may represent energy changes.
Assumptions Assumptions
- Conversions are energy-to-energy only using fixed definitions; no fuel-specific heating values or system losses are included.
- “Calorie” with a capital C (food Calorie) is treated as a kilocalorie (kcal) = 4184 J; 1,000 thermochemical calories equal 1 kcal.
- Unit standards used: cal_th = 4.184 J; cal_IT = 4.1868 J; kcal = 4184 J; BTU (IT) = 1055.05585262 J; BTU (th) = 1054.350264488889 J.
- Results are rounded to a sensible number of decimals for readability.
When to Use This Calculator
- Converting nutrition energy (Calories/kcal) to BTU for HVAC or engineering contexts.
- Standardizing between lab/engineering energy units (calorie variants) and BTU.
- Quick cross-checks when comparing heater specs, fuel charts, or energy budgets.
Input Definitions
- Calories — choose kilocalorie (kcal/Cal = 4184 J), thermochemical calorie (cal_th = 4.184 J), or International Table calorie (cal_IT = 4.1868 J).
- BTU — choose International Table (BTU_IT = 1055.05585262 J) or thermochemical (BTU_th = 1054.350264488889 J).
- Conversions — General: Btu = cal × (J/cal) ÷ (J/Btu). Examples: 1 kcal ≈ 3.965667 BTU_IT; 1 BTU_IT ≈ 0.252164 kcal.
Cal to Btu Formula
The following formulas convert kilocalories (kcal/Cal) to BTU (International Table) and back; Joules are used as the bridge unit.
- 1 kilocalorie (kcal, Cal) = 4184 J
- 1 thermochemical calorie (cal_th) = 4.184 J
- 1 international table calorie (cal_IT) = 4.1868 J
- 1 BTU (International Table) = 1055.05585262 J
- 1 BTU (thermochemical) = 1054.350264488889 J
How do you convert calories to BTU? Pick the calorie type, convert to joules (multiply by J/cal), then divide by J/BTU; for kcal to BTU (IT), multiply kcal by 4184/1055.05585262 ≈ 3.965667.
How do you convert BTU to calories? Multiply BTU by its joule value, then divide by J/cal; for BTU (IT) to kcal, multiply by 1055.05585262/4184 ≈ 0.252164.
Cal to Btu Conversion Table
| Calories (kcal) | BTU (IT) |
|---|---|
| 0.25 | 0.991 |
| 0.50 | 1.983 |
| 1 | 3.966 |
| 1.5 | 5.949 |
| 2 | 7.931 |
| 2.5 | 9.914 |
| 3 | 11.897 |
| 4 | 15.863 |
| 5 | 19.828 |
| 7.5 | 29.743 |
| 10 | 39.657 |
| 12 | 47.588 |
| 15 | 59.485 |
| 20 | 79.313 |
| 25 | 99.142 |
| 30 | 118.970 |
| 40 | 158.627 |
| 50 | 198.283 |
| 75 | 297.425 |
| 100 | 396.567 |
| * For thermochemical kcal to Btu (IT): 1 kcal ≈ 3.965667 BTU. | |
Example Problem
Convert 2.5 kcal (Cal) to BTU (IT).
Use the kcal formula: Btu_IT = kcal × 4184/1055.05585262.
Btu_IT = 2.5 × 4184/1055.05585262 ≈ 9.914 BTU
