The simplest distance conversion for a straight flat putt is 1 inch of backstroke for every foot in the length of the putt. For example, in order to make a 10 foot straight flat putt the backstroke would need to be at least 10 inches. Remember to finish high off your forward foot.
Allowing for an uphill or downhill putt is just as simple. Add an inch to your putt stroke for every inch of elevation change. For example, if you have an uphill putt where the hole is a foot above the ball then add 12 inches to your putt stroke. If the hole is a foot below the hole then subtract 12 inches from your putt stroke.
The stimp meter will alter these calculations so remember your Pace, Path and Putt warm up routine to make any necessary changes to the length of your putt stroke.