Energy Converter – Convert Joules, Calories & BTU

This energy unit converter routes every input through exact definitions — 1 kcal = 4184 J and 1 BTU = 1.05505585 kJ exactly. Enter a value, pick the source and target units, and the result appears instantly with the factor applied shown beside it. Joules and kilojoules are the SI currency of energy, kilocalories price the food you eat, and BTU size the heating and cooling industry — diets, HVAC quotes and physics homework all cross these lines daily. The exchange rates are definitions: 1 kcal = 4184 J exactly by convention and 1 BTU(IT) = 1055.05585262 J, so converter output is limited only by displayed decimals. A mini table of the head factor makes spot-checks immediate: 1 kcal = 4,184 J; 5 kcal = 20,920 J; 10 kcal = 41,840 J; 50 kcal = 209,200 J; 100 kcal = 418,400 J. Anchor the numbers with a snack: one banana (about 105 kcal) delivers roughly 439 kJ, and a 9000-BTU air conditioner moves about 9.5 MJ per hour.

1. 1

   Step 1

   Enter the value you want to convert

2. 2

   Step 2

   Select the source unit you are converting from

3. 3

   Step 3

   Select the target unit you want as the result

4. 4

   Step 4

   Read the exact result, then swap or copy as needed

• 1

  Food anchors: 100 kcal = 418.4 kJ; a 2000-kcal day = 8.368 MJ

• 2

  HVAC shortcut: kW × 3412 = BTU/h

• 3

  EU labels show kJ first — divide by 4.184 for kcal

• 4

  Physics exams want joules: convert kcal × 4184 before substituting

• Using the thermochemical calorie (4.184 J) where the IST calorie (4.1868 J) applies in steam tables

• Reading "Cal" as a small calorie, undercounting food energy 1000-fold

• Comparing a BTU/h rating directly to a kW rating without dividing by 3412