Planck Length

The scale at which gravity and quantum theory meet, and the smallest length with physical meaning.

Specifications & Metrics

symbol

ℓP

status

Measured — CODATA 2022 adjustment

value

1.616255 × 10⁻³⁵ ± 1.8 × 10⁻⁴⁰ m

Relative Scale in Constants

Core Principles & Analysis

• About 1.6 × 10⁻³⁵ m — a proton is 10²⁰ times larger.
• Built from G, ħ and c alone; no experiment can probe it without a quantum theory of gravity.
• A Planck-length black hole evaporates in one Planck time.