Here’s a quick table of how tones generally map to each other between Cantonese and Mandarin:
(I haven’t used tone numbers because it’s impossible to visualise the difference between two Chinese languages if all you can see are digits.)
Notice how both Cantonese rising tones (má, máh) map to the low rising tone of Mandarin, mǎ. And how the low falling tone of Cantonese (mà) counter-intuitively maps to the high rising tone of Mandarin.
The only things that don’t generally map so simply are Cantonese stopped tones (ending in -p, -k or -t) and I haven’t noticed any particular pattern.
However, the rest of the mappings are generally pretty consistent (with the exception of some very common characters), so you can actually guess how to say Mandarin words quite accurately.