Assuming you're looking at a CAA Chart:
Large blue numbers mark the Maximum elevation figures for each "quadrangle" (CAA term -1/2 degree lat/long squares on the 1/2 mill chart). That shows the height AMSL of the highest known feature or terrain.
Add a 1000' safety margin to that , and you get your MSA for that quadrangle.
Of course if you're flying VFR, 500' away from any obstacle will do
