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Energy Converter

Energy is measured in joules (SI), but everyday life uses calories (nutrition), kilojoules (EU labels), watt-hours (electricity bills) and BTU (HVAC). All conversions are exact — the calorie was defined in 1929 as 4.184 J by international agreement.

⚡ Energy Converter

Convert energy units quickly and accurately

0.001

1 J=0.001 kJ

Joule → Kilojoule Table

Joule (J)Kilojoule (kJ)
0.0010.000001
0.010.00001
0.10.0001
10.001
20.002
50.005
100.01
250.025
500.05
1000.1
10001
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Conversion Formulas

  • 1 cal = 4.184 J (exact)
  • 1 kcal = 1,000 cal = 4,184 J = 4.184 kJ
  • 1 Wh = 3,600 J = 3.6 kJ
  • 1 kWh = 3.6 MJ = 860.4 kcal
  • 1 BTU = 1,055.06 J

Common Values

  • 1 food Calorie = 1 kcal = 4.184 kJ
  • 100 kcal = 418.4 kJ
  • 1 kWh = 860 kcal — a daily diet
  • Banana ≈ 105 kcal = 440 kJ
  • Tesla Model 3 battery ≈ 60 kWh

Common Uses

  • Reading EU food labels (kJ + kcal)
  • Diet and fitness tracking
  • Electricity bill analysis
  • Engineering — heating loads (BTU vs kW)
  • Physics homework

Frequently Asked Questions

Is 1 calorie the same as 1 Calorie?

No. 1 food "Calorie" with a capital C = 1 kcal = 1,000 small calories.

How many kJ in 100 kcal?

418.4 kJ. Used on EU food labels.

What is a kWh in joules?

3,600,000 J = 3.6 megajoules.

BTU vs joule?

1 BTU = 1,055.06 J. BTU is still standard in US heating and air-conditioning.

Reviewed by the ConvertProf editorial team. All conversion factors follow internationally agreed standards (SI, ISO, NIST). Spotted an error? Email hello@convertprof.com.
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