Energy is the capacity to do work or produce heat. The SI unit is the joule (J), but different fields stick with their own units: nutrition uses kilocalories, electricity uses kilowatt-hours, heating uses BTU, mechanical engineering uses foot-pounds, and atomic physics uses electronvolts.
Common Conversion Formulas
kWh → joules: multiply by 3,600,000
kWh → BTU: multiply by 3,412.14
kcal → kJ: multiply by 4.184
BTU → joules: multiply by 1,055.06
ft·lb → joules: multiply by 1.35582
eV → joules: multiply by 1.602 × 10⁻¹⁹
MJ → kWh: divide by 3.6
Quick Reference Table
From
To
Value
1 kWh
BTU
3,412.14
1 kWh
MJ
3.6
1 kWh
kcal
860.42
1 kcal
kJ
4.184
1 BTU
J
1,055.06
1 ft·lb
J
1.35582
1 MJ
kWh
0.2778
Common Use Cases
Electricity bills: Utility usage in kWh, appliance ratings in W.
Nutrition: Food Calories (kcal) on labels; some countries list kJ instead.
HVAC: Air-conditioner cooling capacity in BTU/h; furnaces in BTU.
Mechanical engineering: Work and torque in joules or foot-pounds.
Physics: Particle energies in eV, keV, MeV, GeV.
Fuel content: Heating value of gas or oil in MJ or BTU.
Energy Converter is a free browser tool from SimpleCounter. Free online energy converter. Convert joules, calories, kilowatt-hours, BTU, electronvolts, foot-pounds and more. Formulas and reference table included. Enter your values and the result updates as you type — there is nothing to install and no account to create.
Definition: Energy Converter
An energy converter takes the numbers you enter and returns the result using the standard formula for that calculation, so you do not have to work it out by hand.
Key facts
Key facts about Energy Converter
Cost
Free, with no account and no usage limit.
Where the maths happens
In your browser. The values you type are not sent to a server.
Devices
Any modern browser on phone, tablet, laptop or desktop.
Accuracy
Standard published formulas, shown with the units you selected.
Intended use
Estimates for everyday and educational use, not professional advice.
How to use the energy converter
Type your value into the first field.
Choose the unit or option that matches your figures, if the tool offers a choice.
Read the result — it recalculates immediately, with no submit button.
Change any input to compare a second scenario side by side.
Disclaimer: This tool is provided for educational and informational purposes only. Results are estimates based on standard formulas and the inputs you provide. For financial, medical, legal, or tax decisions, consult a qualified professional. See our full disclaimer.
Frequently Asked Questions
How do you convert joules to kilowatt-hours?
Divide joules by 3,600,000. Example: 7,200,000 J ÷ 3,600,000 = 2 kWh. To go the other way, multiply kWh by 3,600,000.
What is the relationship between calories and joules?
1 calorie = 4.184 joules. 1 kilocalorie (food Calorie) = 4,184 joules = 4.184 kJ. Nutrition labels say 'Calories' but mean kilocalories.
How many BTU are in a kilowatt-hour?
1 kWh ≈ 3,412 BTU. Used to compare electric heating with gas furnaces, which are rated in BTU/hour.
How much energy is a food Calorie?
1 food Calorie = 1 kcal = 4.184 kJ. A 2,000-Calorie diet equals about 8,368 kJ or 2.32 kWh of food energy per day.
What is an electronvolt?
1 eV = 1.602 × 10⁻¹⁹ J. It's the energy gained by an electron crossing a 1-volt potential. Used in atomic and particle physics where joules are awkwardly large.
How many joules in a foot-pound?
1 ft·lb = 1.35582 J. Common in US engineering for torque and mechanical work.
How much electricity does running a 100 W bulb for an hour use?
Exactly 0.1 kWh, or 360 kJ, or 360,000 J. At $0.15/kWh that costs about $0.015.
Benefits of using the Energy Converter
What you actually get compared with a mechanical clicker, a notes app, or trying to hold the number in your head.
Nothing to install, nothing to sign up for
Open the energy converter and start counting in the same second. No account, no email, no trial.
Your count survives real life
Totals are saved on your device as you go, so a locked screen, a closed tab, or a lost signal does not reset anything.
Works offline once loaded
Install it to your home screen and it keeps working in a warehouse, a pool hall, a field, or a plane — no connection needed.
Private by default
Counts stay in your browser. There is no cloud sync, no profile, and nothing about what you count is sent to us.
Free, with no sign-up
Works offline once loaded
Counts stay on your device
Installable as an app
Runs in your browser — nothing to download
72+ counter types available
Share your setup
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