J SI derived
Measures: Energy — how much work can be done
Joule
The SI energy unit — lifting a small apple one metre.
EnergyHow it's defined
Defined as one newton acting through one metre (N·m), equivalently one watt for one second. All energy — motion, heat, electricity, food — meets in this unit.
1 J = 1 N·m = 1 W·s — exact1 kJ = 1,000 J — exact
Convert — honestly
J equals
0.239005736 cal
Calorie (thermochemical) · factor exact — exact by definition (thermochemical)
2.7778e-7 kWh
Kilowatt-hour · factor exact — exact by definition
Conversions run through the joule using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- Elementii — ionization energies are kJ/mol ↗ open elementii
- Food energy underneath the calorie label
Other ways to measure energy
Source
This page is an authored summary of the authoritative definition — checkable one click away.
BIPM — The International System of Units (SI Brochure, 9th ed.)