Energy Converter — Joules, kWh, BTU
Convert between joules, kilojoules, calories, kilocalories, BTU, kWh, and electron volts.
What Is the Energy Converter — Joules, kWh, BTU?
The Energy Converter converts between all major energy units: joules (J), kilojoules (kJ), calories (cal), kilocalories (kcal), kilowatt-hours (kWh), British Thermal Units (BTU), megajoules (MJ), and electronvolts (eV). Used in physics, nutrition, thermodynamics, and electrical engineering.
Formula
How to Use
Enter an energy value in any supported unit. The converter instantly displays all equivalent values simultaneously. Common conversions include joules to calories (for nutrition), kWh to joules (for electricity), BTU to kJ (for HVAC), and eV to joules (for atomic physics).
Example Calculation
2000 kcal (daily food energy): = 2000×4184 = 8,368,000 J = 8.368 MJ = 2.324 kWh = 7931 BTU. 1 kWh of electricity: = 3,600,000 J = 860 kcal = 3412 BTU = 3.6 MJ.
Understanding Energy Converter — Joules, kWh, BTU
Energy is the capacity to do work, and it appears in many forms — thermal, electrical, chemical, kinetic, potential, and nuclear — each with its own traditional measurement unit. The SI unit is the joule (J = kg·m²/s²), but different fields use units suited to their typical scales: kilowatt-hours for electrical energy, kilocalories for food energy, BTUs for HVAC, and electronvolts for atomic-scale physics.
Energy conversion efficiency is a central concept in thermodynamics: power plants convert chemical or nuclear energy to electricity at 30–50% efficiency; the rest is waste heat. Electric motors convert electrical energy to mechanical energy at 85–97% efficiency. The human body converts food energy to mechanical work at about 25% efficiency.
Understanding energy units and conversions is essential for nutritional analysis (food energy), utility bill comprehension (electricity kWh, gas BTU), building energy modeling (HVAC BTU/hr), renewable energy system design (kWh/day solar production), and scientific research (eV in spectroscopy and semiconductor physics). This converter handles the full range from subatomic to industrial scales.
Frequently Asked Questions
What is the difference between calorie (cal) and Calorie (kcal)?
1 food Calorie (capital C) = 1 kilocalorie = 1000 small calories. Nutrition labels always use kilocalories (kcal), often written as 'Calories.' 1 cal = energy to raise 1g water by 1°C; 1 kcal raises 1 kg of water by 1°C.
How is electrical energy measured in kWh related to joules?
1 kWh = 1000W × 3600 seconds = 3,600,000 J = 3.6 MJ. Your electricity bill charges per kWh consumed. A 1kW appliance running for 1 hour uses 1 kWh.
What is an electronvolt (eV) used for?
The electronvolt is the energy gained by one electron moving through 1 volt potential difference: 1 eV = 1.602×10⁻¹⁹ J. Used in atomic physics, particle physics, and semiconductor engineering (band gap energies).
What energy unit does the body use?
Nutritional energy is measured in kilocalories (kcal or Cal). A typical adult needs 2000–2500 kcal/day. In many countries, food labels show both kcal and kJ.
Is this converter free?
Yes, completely free with no registration required.
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