Hi there. I would like to know where I can find information about intonation math.
Thanks

Google is your friend...

What intonation math? Most intonation is set by comparing the 12th fret octave harmonic to the fretted 12th fret octave: compared to the harmonic octave, if the fretted octave intonations sharp, screw the saddle backwards; if the octave intonates flat, screw the saddle forwards.

Now, where to approximately set the saddles before fine tuning: screw each saddle backwards by approximately the diameter of a wound string, or the core of a wound string.

That is why, for instance, for those who use conventional plain-3rd G-string sets the D string saddle forward while the plain G saddle is more to the rear.

Thanks for answering. Sorry. I used the wrong word, math. I should have written just for help. I have made intonation with my several guitars as well as others and, yes, it´s a trial and error procedure. If the sounds in the 12 th fret are not similar you just move the saddles, backward or forward.
I have noticed several things. If the strings are old, when I change them for newer ones the intonation changes. The same happens when I change, say, medium gauge strings for light or ultralight strings. Different brands and models have different distances between nut and bridge and between frets. In a 6 or 12 string electric guitar you just move the saddles for a correct intonation.
But in an acoustic guitar you just depend on a correct design. I have used electric guitar strings for an acoustic, and Phosfor bronze too and the intonation changes. So, I guess the string material affects. I have put pieces of plastic or bone in the bridge nut position to compensate for a good intonation because the nut is fixed. Some comercial nuts are made with a curved line, wich is ok, but just for the 5 th string only the position of the line in the nut is different from the other ones. I don´t know the reason.
My question should have been probably for main factors that affect intonation.
Thanks in the hope to learn more about of this issue.

I made a typing error. On the rough set, back the saddles by the diameter of the plain string for the E, B, and G if plain, and the diameter of the core of G, if wound, D, A, and E. Sorry about mistyping.