How to calculate Percent Solvent Accesibility from Residue Solvent Accessibiblity?

Hello,
I want to know that
How to calculate Percent Solvent Accessibility from Residue Solvent Accessibility?
It seems relative values about residue solvent accessibility per maximum solvent accessibility.
If true, I want to know maximum solvent accessibilities for all 20 residues...
Please, let me know more information about solvent accessibilities...