I don't use formulas so to speak, but word of caution, be careful on DH putts and be firm on uphill putts.
I/e a 10 foot 3 inch DH putt on T greens that you normally hit with X power, play it like a 8 foot putt...now the 10 foot 3inch up hill putt, play it as you would T greens, but just maybe a scooch less...or just as firm and find a good line.
Sorry, not very scientific, just how I do it.