β‘ Energy Converter
Joules, calories, kWh, BTU, and electronvolts with live conversion.
All energy units
How to Use This Energy Converter
Enter an energy amount, choose its unit, and see every equivalent instantly. Whether you are reading a nutrition label, comparing utility bills, or doing physics homework, this tool bridges the three worlds of energy units: scientific (joules), nutritional (calories), and practical (kWh, BTU).
Type the energy value into the field.
Pick the starting unit from the dropdown.
Read all converted units in the results panel.
Energy Units Explained
The joule is the SI unit of energy: one joule lifts a small apple about one meter. Calories come from chemistry: one calorie heats one gram of water by one degree Celsius. Food energy is measured in kilocalories (1,000 calories), confusingly labeled just "Calories" with a capital C on US nutrition labels.
Kilowatt-hours are how electricity is billed: running a 1,000-watt appliance for one hour uses 1 kWh. BTU (British Thermal Unit) dominates US heating and cooling: one BTU heats one pound of water by one degree Fahrenheit, and air conditioners are rated in BTU per hour. Electronvolts belong to atomic physics, and therms (100,000 BTU) are how natural gas is billed.
Key Conversion Factors
These factors are exact by definition except the calorie, which has several historical variants. This converter uses the thermochemical calorie (4.184 J), the standard in nutrition and chemistry.
Worked Example
Your electric bill says you used 900 kWh last month. In joules: 900 Γ 3,600,000 = 3.24 billion joules. In BTU: 900 Γ 3,412 = 3,070,800 BTU, or about 30.7 therms, letting you compare electric versus gas heating costs directly. As food energy, 900 kWh equals 774,000 kcal, roughly 387 days of food for one person.
Practical Context
A typical US home uses 800 to 1,000 kWh of electricity per month. A gas furnace might burn 50 therms in a cold month. Running a 1,500-watt space heater for 8 hours uses 12 kWh, which at 15 cents per kWh costs $1.80. Understanding these units turns confusing bills into plain arithmetic.
Frequently Asked Questions
How many joules are in a food Calorie?
4,184 joules. Food Calories are kilocalories (1,000 physics calories), and one thermochemical calorie equals 4.184 joules. A 200-Calorie snack contains 836,800 joules.
How do I convert kWh to BTU?
Multiply kWh by 3,412. So 1 kWh = 3,412 BTU. This is useful for comparing electric heating costs with gas furnace ratings, which are usually given in BTU.
What is the difference between a calorie and a Calorie?
A physics calorie (lowercase) is the energy to heat 1 gram of water by 1Β°C. A food Calorie (uppercase C) is 1,000 physics calories, properly called a kilocalorie. Nutrition labels always mean kilocalories.
How many BTU are in a therm?
100,000 BTU. Natural gas is billed in therms in the US, so a 50-therm winter gas bill represents 5,000,000 BTU of heating energy.
What is a kilowatt-hour in simple terms?
The energy used by a 1,000-watt appliance running for one hour. Ten 100-watt bulbs burning for one hour also use 1 kWh. It is the standard unit on electricity bills worldwide.