Read the tipps behind Icon's link!
Survivorman:For example, I'm a tour pro, let's say I
have a 25 ft putt and it's all yellow. how do I calculate where I should
putt from?
The regular green speed for Tour Pros is "very fast".
Thus, the ball runs approx. 20% longer than the scales say and the rule
of thumb says, add/substract one foot length for three inches
elevation. (both numbers subject to change for other green speeds).
It's not enough to know up or down, the range counts!
So,
if it is 20 inches down, subtract 7 feet from the distance, hit the
ball 18 ft / 1.2 = 15 ft which is 50% on a 30 ft scale. Since "yellow"
is very steep, I'd start with an additional 1 or 2 ft less.
And, next time you might want to keep the approach below the hole which makes putting much easier ;)