energy · Scientific legacy · Modern/historical

erg

exact

Definition

1 erg = 10⁻⁷ J

One erg is exactly 1 × 10⁻⁷ joules.

The erg belongs to the centimetre–gram–second system and was widely used in scientific work before SI energy units became dominant.

Modern use is context-dependent and varies by region or measurement system.

Source tier — · confidence high

energy · International · Modern

SI derived unit of energy and work; 1 J = 1 N·m = 1 kg·m²·s⁻².

cal

energy · International · Modern / historical

The generic calorie is variant-dependent; NIST lists thermochemical, International Table, mean, 15 °C, and 20 °C calories.

variant

kcal

energy · International · Modern / historical

A kilocalorie is 1000 calories, so its joule value depends on the calorie convention.

variant

Btu

energy · International · Modern / historical

British thermal unit is variant-dependent; NIST lists IT, thermochemical, mean, and temperature-specific forms.

variant

energy · International · Modern / historical

Non-SI unit accepted for use with the SI; 1 eV = exactly 1.602176634×10⁻¹⁹ J.

kW·h

energy · International · Modern

1 kWh = exactly 3.6×10^6 J.

cal_th

energy · International · Modern

calorie (thermochemical): 1 unit = 4.184 J.

cal_IT

energy · International · Modern

calorie (International Table): 1 unit = 4.1868 J.