National Institute of Standards and Technology

Computational Chemistry Comparison and Benchmark DataBase
Release 22	May 2022
NIST Standard Reference Database 101

I	Introduction
II	Experimental data
III	Calculated data
IV	Data comparisons
V	Cost comparisons
VI	Input and output files
VII	Tutorials and Units
VIII	Links to other sites
IX	Feedback
X	Older CCCBDB versions
XII	Geometries
XIII	Vibrations
XIV	Reaction data
XV	Entropy data
XVI	Bibliographic data
XVII	Ion data
XVIII	Bad calculations
XIX	Index of properties
XX	H-bond dimers
XXI	Oddities

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VII.D.3.

Converting between rotational constants and moments of inertia

Rotational constants are inversely related to moments of inertia:

B = h/(8 π² c I)

Where B is the rotational constant (cm^-1)
h is Plancks constant (gm cm²/sec)
c is the speed of light (cm/sec)
I is the moment of inertia (gm cm²)

Enter a rotational constant or a moment of inertia in the appropriate box below and press the adjacent calculate button. The related quantities will appear in the other boxes.

B		cm-1
B		GHz
B		MHz
I		gm cm2
I		amu Å2