Energy Unit Converter

Convert between Joules, Calories, and electronvolts (eV). Essential for physics, chemistry, nutrition science, and engineering calculations.

Calorie Standard:

Input Value

From Unit

To Unit

Conversion Result

418.4 J

Intermediate value: 100 cal (thermochemical)

Decimal Places

About Energy Conversions

Energy measurements are fundamental in physics, chemistry, and engineering. This converter handles three key units:

Joule (J): SI unit of energy (kg·m²/s²)
Calorie (cal): Energy needed to raise 1g of water by 1°C (varies by standard)
Electronvolt (eV): Energy gained by an electron moving through 1V potential (1.602×10⁻¹⁹J)

Examples

100 J ≈ 23.9 cal (thermochemical) ≈ 6.242×10²⁰ eV
500 cal (international) ≈ 2093.4 J ≈ 1.306×10²² eV
1 eV ≈ 1.602×10⁻¹⁹ J ≈ 3.826×10⁻²⁰ cal

Reference Table

Unit	Joules	Calories (thermochemical)	Electronvolts
1 J	1	0.239	6.242×10¹⁸
1 cal	4.184	1	2.611×10¹⁹
1 eV	1.602×10⁻¹⁹	3.826×10⁻²⁰	1

Note on Precision: The electronvolt conversion uses the exact 2019 SI definition. Calorie conversions vary by standard - always specify which definition you're using.

Energy Context Helper

See how your converted energy compares to common physical phenomena:

Reference Energy

Comparison Result

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Frequently Asked Questions

Why are there different calorie definitions?

Different experimental measurements of the energy required to heat water produced slightly different results. The thermochemical calorie (4.184 J) is most common in chemistry.

How precise is the eV conversion?

The electronvolt is now defined exactly as 1.602176634×10⁻¹⁹ J since the 2019 SI redefinition.

When should I use joules vs calories?

Joules are the SI unit and preferred in most scientific contexts. Calories are still commonly used in nutrition and chemistry.

Formulas & Assumptions

Conversion formulas:
1 thermochemical cal = 4.184 J (exactly)
1 international steam table cal = 4.1868 J
1 15°C cal = 4.1858 J
1 eV = 1.602176634×10⁻¹⁹ J (exact)

All conversions calculated through joules:
Target = (Input × FromUnitInJoules) / ToUnitInJoules

Rounding: Banker's rounding to selected decimal places

Disclaimer: For educational and informational purposes only. Not intended for critical engineering, medical, or scientific applications. Always verify results with authoritative sources.

Sources & References

SI Brochure: The International System of Units (9th edition)
NIST Special Publication 811: Guide for the Use of the International System of Units
IUPAC Gold Book: Definitions of thermodynamic terms
CODATA Internationally Recommended Values of the Fundamental Physical Constants

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Energy Unit Converter Joules Calories eV

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