Energy Converter

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Joule • kWh • calorie • BTU • therm

Energy Value ⓘ

From

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Enter an energy value to convert

How to Use the Energy Converter

Enter an energy value — e.g. 1 for 1 kWh of electricity, or 500 for a 500-Calorie meal.
Select From unit — kWh (electric bills), kcal/Calories (food), BTU (HVAC/heating), joules (physics), therms (natural gas).
Read the result — joules, kWh, food Calories, and BTU all show at once.
Watch the units — a food "Calorie" (capital C) is a kilocalorie (kcal) = 1,000 small calories. Nutrition labels mean kcal.

Benefits

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Electricity Bills

US utilities bill per kWh (avg ~16¢/kWh in 2026). Convert appliance joules or watt-hours to kWh to estimate running costs.

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Food Energy

Nutrition labels list food Calories (kcal). Convert to joules (the SI unit used outside the US) when reading international labels.

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Heating & HVAC

Furnaces and AC are rated in BTU. Natural gas bills use therms. Convert to kWh to compare energy sources fairly.

Energy Conversion Guide — Joules, kWh, Calories, BTU

Energy comes in many units depending on context, and the joule (J) is the SI base unit that ties them all together. For US households, the most useful conversion is to kilowatt-hours (kWh): 1 kWh = 3,600,000 joules = 3.6 megajoules. Your electricity bill is measured in kWh, and at the 2026 US average of about 16 cents per kWh, knowing how to convert appliance energy ratings helps estimate running costs. A 1,500-watt space heater run for one hour uses 1.5 kWh = 5.4 million joules ≈ 24 cents.

For food, the "Calorie" on nutrition labels is actually a kilocalorie (kcal) = 4,184 joules. A 2,000-Calorie daily diet equals 8.37 million joules of energy. In heating and cooling, the British Thermal Unit (BTU) dominates US specs: 1 BTU = 1,055 joules, and 1 kWh = 3,412 BTU. Natural gas is billed in therms, where 1 therm = 100,000 BTU = 29.3 kWh = 105.5 million joules. Understanding these relationships lets you compare the true cost and efficiency of electricity, gas, and other energy sources on equal footing.

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Appliance Energy Use

LED bulb (10W, 1hr): 0.01 kWh. Laptop (50W, 8hr): 0.4 kWh. Refrigerator: ~1.5 kWh/day. Central AC: 3 kWh/hr. EV charge (full): 50–100 kWh.

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Energy Content

1 gallon gasoline: ~33.7 kWh (121 MJ). 1 cubic foot natural gas: ~0.3 kWh. AA battery: ~0.004 kWh. Tesla Model 3 battery: ~60 kWh.

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Food Energy

Apple: 95 kcal = 397 kJ. Slice of pizza: 285 kcal. Big Mac: 563 kcal = 2,356 kJ. Daily diet: 2,000 kcal = 8.4 MJ. 1 lb of fat ≈ 3,500 kcal.

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HVAC & Heating

1 BTU = 1,055 J. Window AC: 5,000–12,000 BTU/hr. Furnace: 40,000–100,000 BTU/hr. 1 therm natural gas = 29.3 kWh.

Energy Conversion FAQ

How many joules in a kWh? ▾

1 kilowatt-hour (kWh) = 3,600,000 joules = 3.6 megajoules (MJ). This is because 1 watt = 1 joule per second, so 1,000 watts × 3,600 seconds = 3,600,000 joules. Your electricity meter measures kWh because joules would be inconveniently large numbers for billing.

Is a food Calorie the same as a calorie? ▾

No — and this confuses many people. A food "Calorie" (capital C, as on nutrition labels) is actually a kilocalorie (kcal) = 1,000 small calories (lowercase c). So a 100-Calorie snack = 100 kcal = 100,000 calories = 418,400 joules. Scientists use the small calorie (4.184 J); nutritionists use the kcal. This converter handles both.

How do I convert BTU to kWh? ▾

1 BTU = 0.000293071 kWh, and 1 kWh = 3,412.14 BTU. To convert a heating/cooling appliance: divide its BTU rating by 3,412 to get kW. A 12,000 BTU/hr air conditioner = 3.517 kW. This lets you compare gas heating (often in BTU) with electric heating (in kWh) for cost analysis.

What is a therm and how does it relate to kWh? ▾

A therm is a unit of heat energy used for natural gas billing in the US: 1 therm = 100,000 BTU = 29.3 kWh = 105.5 megajoules. The average US home uses 40–80 therms per month for heating in winter. At ~$1.50/therm, converting to kWh (29.3 kWh per therm) lets you compare the cost of gas heating versus an electric heat pump.