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Energy Conversion Calculator

Convert energy between joules, watt-hours, kilowatt-hours, BTU, calories, and therms.

Formula shown0 inputs definedFree, no sign-up

Quick Summary

Use this when you need:

Convert electric bills from kWh into BTU or therms
Compare heating fuels quoted in BTU with lab data given in joules
Translate nutrition calories into watt hours for science projects

You’ll get:Energy

How this is calculated

Formula:

energy_target = energy_source * (source_to_joules / target_to_joules)

In plain language:

We treat joules as the base, so every quantity is converted into joules first and then divided by the target unit's joule equivalent.

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Energy

Energy used in the calculation.

When to use this calculator

Convert electric bills from kWh into BTU or therms
Compare heating fuels quoted in BTU with lab data given in joules
Translate nutrition calories into watt hours for science projects

Last updated: November 18, 2025

Energy conversion explained

Utility bills show kilowatt-hours, HVAC contractors speak in BTU, and labs usually prefer joules. The Energy Conversion Calculator normalizes every number into joules, then scales it into the unit your stakeholders expect so you can compare fuels, appliances, and lab data without retyping constants.

How the conversion works

Each energy unit has an exact joule equivalent (e.g., $1\,\text{kWh} = 3.6\times10^6\,\text{J}$ , $1\,\text{BTU} = 1{,}055.06\,\text{J}$ , $1\,\text{therm} = 105{,}505{,}585\,\text{J}$ ). The calculator always performs:

\text{target} = \text{source} \times \frac{k_{\text{source}\to J}}{k_{\text{target}\to J}}

That means you can hop directly between kWh, BTU, calories, joules, therms, or megajoules without chaining intermediate steps.

Units and conversions

Unit	Relation
Joule (J)	Base SI energy unit
Watt-hour (Wh)	$1\,\text{Wh} = 3{,}600\,\text{J}$
Kilowatt-hour (kWh)	$1\,\text{kWh} = 3.6\times10^6\,\text{J}$
BTU	$1\,\text{BTU} = 1{,}055.06\,\text{J}$
Therm	$1\,\text{therm} = 105{,}505{,}585\,\text{J}$
Calorie (cal)	$1\,\text{cal} = 4.184\,\text{J}$ (kcal = 4,184 J)

Worked examples

Electric bill to BTU
Convert 12 kWh of electric heat to BTU for an HVAC load sheet.

12\,\text{kWh} \times 3{,}412.14 \frac{\text{BTU}}{\text{kWh}} = 40{,}946\,\text{BTU}

Result: roughly 41k BTU.

Furnace spec to kWh
A gas heater outputs 50,000 BTU per hour. Express that in kWh for an energy dashboard.

\text{kWh} = \frac{50{,}000}{3{,}412.14} \approx 14.65

Result: about 14.7 kWh.

Tips and pitfalls

Keep everything in joules when combining multiple fuels or storage technologies; convert outward only for reporting.
Distinguish between therm (natural gas billing) and MMBtu (industrial fuel). Both stem from BTU but differ by a factor of 10.
Nutrition "Calories" on food labels are kilocalories; use the kcal unit to avoid a 1,000× mistake.
When comparing electricity to thermal fuels, add system efficiency to the conversation—resistance heat is nearly 100% efficient, while combustion appliances may be 80–95%.

References and further reading

Frequently Asked Questions

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Calculator info

Version:: v1.0.0
Sensitivity:: low
References:: 1

Last updated: November 18, 2025

Energy conversion explained

How the conversion works

\text{target} = \text{source} \times \frac{k_{\text{source}\to J}}{k_{\text{target}\to J}}

That means you can hop directly between kWh, BTU, calories, joules, therms, or megajoules without chaining intermediate steps.

Units and conversions

Unit	Relation
Joule (J)	Base SI energy unit
Watt-hour (Wh)	$1\,\text{Wh} = 3{,}600\,\text{J}$
Kilowatt-hour (kWh)	$1\,\text{kWh} = 3.6\times10^6\,\text{J}$
BTU	$1\,\text{BTU} = 1{,}055.06\,\text{J}$
Therm	$1\,\text{therm} = 105{,}505{,}585\,\text{J}$
Calorie (cal)	$1\,\text{cal} = 4.184\,\text{J}$ (kcal = 4,184 J)

Worked examples

Electric bill to BTU
Convert 12 kWh of electric heat to BTU for an HVAC load sheet.

12\,\text{kWh} \times 3{,}412.14 \frac{\text{BTU}}{\text{kWh}} = 40{,}946\,\text{BTU}

Result: roughly 41k BTU.

Furnace spec to kWh
A gas heater outputs 50,000 BTU per hour. Express that in kWh for an energy dashboard.

\text{kWh} = \frac{50{,}000}{3{,}412.14} \approx 14.65

Result: about 14.7 kWh.

Tips and pitfalls

Keep everything in joules when combining multiple fuels or storage technologies; convert outward only for reporting.
Distinguish between therm (natural gas billing) and MMBtu (industrial fuel). Both stem from BTU but differ by a factor of 10.
Nutrition "Calories" on food labels are kilocalories; use the kcal unit to avoid a 1,000× mistake.
When comparing electricity to thermal fuels, add system efficiency to the conversation—resistance heat is nearly 100% efficient, while combustion appliances may be 80–95%.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Energy

When to use this calculator

Energy conversion explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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Calculator info

Energy conversion explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

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