Planck length
UniversalMeasured
= 1.616 255(18) × 10−35 m
- Value
- 1.616 255 × 10−35 m
- Standard uncertainty
- 1.8 × 10−40 m
- Relative uncertainty
- 1.1 × 10−5 (11 parts per million)
- Status
- Measured
- Symbol
- Source
- CODATA 2022 via NIST · NIST entry
Use in a calculation
# Planck length, CODATA 2022 (NIST)
planck_length = 1.616255e-35 # m, standard uncertainty 1.8e-40
# SciPy: scipy.constants.physical_constants['Planck length']What it is
The unit of length built from G, ħ and c alone. Far below anything measurable, it marks roughly where quantum effects of gravity are expected to matter. Its uncertainty comes entirely from G.
Equations
- definition
In other units
| Unit | Value | |
|---|---|---|
| CGS (cm) | 1.616 255 × 10−33 |
Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display. The relative uncertainty is unchanged by conversion to an exactly defined unit.
How the value changed, 1998–2022
Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).
Relative uncertainty
| CODATA | Value (uncertainty) | Relative uncertainty | Change from previous |
|---|---|---|---|
| 2022 | 1.616 255(18) × 10−35 | 1.1 × 10−5 | +0.0 σ of 2018 |
| 2018 | 1.616 255(18) × 10−35 | 1.1 × 10−5 | +0.7 σ of 2014 |
| 2014 | 1.616 229(38) × 10−35 | 2.4 × 10−5 | +0.3 σ of 2010 |
| 2010 | 1.616 199(97) × 10−35 | 6.0 × 10−5 | −0.7 σ of 2006 |
| 2006 | 1.616 252(81) × 10−35 | 5.0 × 10−5 | +0.1 σ of 2002 |
| 2002 | 1.616 24(12) × 10−35 | 7.4 × 10−5 | +0.2 σ of 1998 |
| 1998 | 1.6160(12) × 10−35 | 7.4 × 10−4 |
“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).