Hartree energy = 4.359 744 722 2060 × 10⁻¹⁸ J

Name: Hartree energy — CODATA 2022 value
Creator: NIST

Value: 4.359 744 722 2060 × 10⁻¹⁸
Unit: J
Uncertainty: 0.000 000 000 0048 × 10⁻¹⁸
Copy-ready: 4.3597447222060e-18

The Hartree energy Eₕ, twice the ionisation energy of an idealised hydrogen atom and the atomic unit of energy.

Quantum-chemistry programs print energies in hartrees; multiply by this value for joules, or use the eV line beneath.

Also listed by NIST as: Atomic unit of energy — the same value and unit.

The same quantity, other ways NIST lists it

Quantity (NIST name)	Value	Unit	Uncertainty
Hartree energy in eV	27.211 386 245 981	eV	0.000 000 000 030

NIST, Fundamental Physical Constants — Complete Listing (2022 CODATA adjustment), retrieved 2026-07-26.

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The same quantity, other ways NIST lists it

Electrical, thermal and X-ray constants

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