Natural unit of time = 1.288 088 666 44 × 10−21 s

Value
1.288 088 666 44 × 10−21
Unit
s
Uncertainty
0.000 000 000 40 × 10⁻²¹
Copy-ready
1.28808866644e-21

The natural unit of time in the system where ℏ, c and the electron mass equal 1.

Used in relativistic quantum mechanics; multiply a result in natural units by this value to get the time in SI.

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

Natural units and Planck units

Planck lengthPlanck massPlanck temperaturePlanck timeNatural unit of momentumNatural unit of time

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UsePhysics. "Natural unit of time — 1.288 088 666 44 × 10−21 s." UsePhysics.com. https://usephysics.com/reference/natural-unit-of-time. Value from the 2022 CODATA adjustment (NIST). Accessed [date].

All physical constants

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