PhysicsCalcs
Electricity

Energy Conversion Calculator

Convert joules, kilojoules, watt-hours, kilowatt-hours, calories, BTU, therms, electronvolts, horsepower-hours, and other energy units.

Interactive calculator

Energy Conversion Calculator

Convert joules, kWh, BTU, calories, electronvolts, and more.

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Results

Enter a value and click Convert to see the conversion.

Quick Guide

  • Enter a value and select the source unit.
  • Two units mode (default) converts between any pair.
  • Use All units mode to see every equivalent.
  • Try quick presets like 1 kWh → J.

Table of Contents

Key Takeaways

  • The joule (J) is the SI unit of energy.
  • 1 kWh = 3,600,000 J = 3.6 MJ.
  • 1 Wh = 3,600 J.
  • 1 kcal = 4,184 J (thermochemical calorie; 1 food Calorie = 1 kcal).
  • 1 BTU (IT) ≈ 1,055.06 J.
  • Energy and power are different: kW is power; kWh is energy.

What Is an Energy Conversion Calculator?

It converts one energy unit into another using joules as the internal reference. Useful for physics, electricity, heating, engineering, and science education.

For power (rate of energy transfer), use the Watts Calculator or Electrical Power Calculator.

Common Energy Conversion Formulas

1Wh=3600J1 Wh = 3600 J
1kWh=3.6×106J1 kWh = 3.6 × 10⁶ J
1kcal=4184J1 kcal = 4184 J
1eV=1.602176634×10−19J1 eV = 1.602176634 × 10⁻¹⁹ J

Joules to kWh Formula

1 kWh = 1000 Wh = 3.6 MJ. To convert joules to kWh, divide by 3,600,000. Kilowatt-hours are standard for electricity billing; joules are the SI unit.

kWh=J/3,600,000kWh = J / 3,600,000

BTU to kWh

1 BTU (IT) ≈ 1,055.06 J. To convert BTU to kWh, divide BTU by about 3,412.14 (since 1 kWh = 3.6 MJ).

Calorie vs Kilocalorie (Food Calorie)

The small calorie (cal) used in chemistry is the thermochemical calorie: 4.184 J. The food Calorie (capital C) equals 1 kilocalorie (kcal) = 4,184 J. An International Table calorie (4.1868 J) is listed separately for HVAC and older references.

Electronvolt to Joule

1 eV = 1.602176634 × 10⁻¹⁹ J (CODATA 2019). Electronvolts are convenient for atomic and nuclear physics; multiply by 1.602 × 10⁻¹⁹ to get joules.

Energy vs Power

Energy (J, Wh, kWh) is the total amount used or stored. Power (W, kW) is the rate of energy transfer. Power × time = energy.

Examples

1 kWh

1 kWh = 3,600,000 J = 3.6 MJ.

1000 BTU

1000 BTU (IT) ≈ 1,055,056 J ≈ 0.293 kWh.

1 MeV

1 MeV = 1.602 × 10⁻¹³ J.

1000 kcal

1000 kcal = 4.184 MJ.

Limitations

Uses fixed conversion factors. BTU and calorie definitions are specified (IT BTU, thermochemical calorie). Gas volume is not converted to energy without heating value. Utility billing may use local corrections. Dekatherm and MMBtu are treated as equivalent in US gas billing.

FAQ

What is the SI unit of energy?›

The joule (J) is the SI unit of energy.

How many joules are in 1 kWh?›

1 kWh = 3,600,000 J = 3.6 MJ.

How do I convert joules to kWh?›

Divide joules by 3,600,000. Example: 3,600,000 J = 1 kWh.

How many joules are in 1 BTU?›

1 International Table BTU ≈ 1,055.05585262 J.

Which calorie definition does this calculator use?›

The thermochemical calorie (4.184 J) is the default cal unit. An International Table calorie (4.1868 J) is also available separately.

Is kW the same as kWh?›

No. kW is power (rate). kWh is energy (amount over time). See the Watts Calculator for power conversions.

What is an electronvolt?›

1 eV = 1.602176634 × 10⁻¹⁹ J, used in atomic and particle physics.

Can I convert gas therms to kWh?›

Yes, using energy units directly. 1 US therm ≈ 29.3 kWh. This tool does not convert gas volume (cubic feet) to energy.

Can I convert gas cubic feet to kWh?›

Not in this tool. Gas volume to energy requires a heating-value assumption and is excluded.

Sources

  1. NIST: SI Units
  2. CODATA: electron volt
Manish Kumar

Author & technical reviewer

Manish Kumar

PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.

Learn more about Manish