Favor is calculated as the square root of all your all your added temple levels for the God you worship. i.e, you have 3 cities worshiping Zeus with temple levels 25, 13 and 19. Your favor for Zeus will then be the square root of 25+13+19 or 7.5/hour.
Formula: Game speed x (square root of (building levels + devine statues)
Example 2: So lets say you have one level 25 temple, one lvl 14 temple and one divine statue(statue counts as 5 levels) on a speed 1 world. The formula would be:
= Game speed(1) x (square root of (25 +14 +5))
= Game speed(1) x (square root of 44)
= Game speed(1) x 6.6
= 1 x 6.6
= 6.6 favor per hour