Conventional value of coulomb-90

$C_{90}$ = 1.000 000 088 87… C

Value: 1.000 000 088 87… C
Standard uncertainty: exact
Relative uncertainty: exact
Status: Exact
Symbol: $C_{90}$
Source: CODATA 2022 via NIST · NIST entry

NIST prints this exact value cut to 12 digits. ConstantID recomputes it from the defining constants: 1.000 000 088 871 438 104 918 01…

Use in a calculation

# conventional value of coulomb-90, CODATA 2022 (NIST)
conventional_value_of_coulomb_90 = 1.00000008887143810491801  # C, exact

# SciPy: scipy.constants.physical_constants['conventional value of coulomb-90']

What it is

The size of the practical coulomb used in electrical metrology from 1990 to 2019 (based on K_J-90 and R_K-90), in SI coulombs. It is exact because the elementary charge and Planck constant are now exact.

It is built only from constants with exact values, so it is exact too.

In other units

Unit	Value
mC millicoulomb	1000.000 089	exact
µC microcoulomb	1 000 000.089	exact
mA·h milliampere hour	0.277 777 8025	exact

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.

How the value changed, 1998–2022

CODATA	Value (uncertainty)	Relative uncertainty	Change from previous
2022	1.000 000 088 87…	exact	exact
2018	1.000 000 088 87…	exact

“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).