algorithm for molecular 'dimensions'

[gyromagnetic]

Hi,
I am interested in computing the 'dimensions' of molecules from
information contained in a file (e.g. mol2, sdf). By 'dimensions', I
mean roughly the length, depth, and cross-sectional area of the
molecule.

Does anyone have software, or an algorithm (or citation for an
algorithm) to compute such properties?

Any suggestions are appreciated.

-gyro

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