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energy · International · Modern / historical

British thermal unit

Btuvariant
Record
M326
Definition quality
Variant-dependent
Conversion mode
variant selection
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Variant selection required

Definition

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

Reference value

See variants

History & use

Parent concept; users must select a documented variant.

Modern use

Modern-use scope is context-dependent; the website should follow the record's current-status and regional/system labels rather than imply universal use.

Did you know?

Small BTU variant differences become meaningful at large scales.

Documented variants

Sources & evidence

Source tier Tier A · confidence High

Related measurements

joule

J

energy · International · Modern

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

calorie

cal

energy · International · Modern / historical

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

variant

kilocalorie

kcal

energy · International · Modern / historical

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

variant

electronvolt

eV

energy · International · Modern / historical

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

kilowatt-hour

kW·h

energy · International · Modern

1 kWh = exactly 3.6×10^6 J.