rRNA bands - kb size equivalent on gel?

[Wendy Ingram]

Hi,

I would like to find out what size (in kilobases) Ribosomal RNA bands
run equivalent to on an agarose gel.  I'd like to use their positions as
a rough quide to where I should expect a probe to bind on a Northern
that was run without an RNA ladder.

Thanks,

Wendy Ingram.