Sure! Here's the trigonometry of length and lie:
First, adopt your best setup posture AS IF holding a putter. Then use a tape measure or string to measure straight down from the center of your grip / hands to the ground directly beneath (Measurement B). Then measure from this point on the ground out to the spot where you comfortably face and aim your eyes straight out of your face as if looking at your perfect putter's sweetspot (measurement A).
With these two numbers, you calculate length as follows:
A*A + B*B = C*C, where C is the length from center of hands to ground where ball would be at sweetspot. So, the SQUAREROOT of (A*A + B*B) is this number in inches. Add 4 inches to this and your hands should then end up in the middle of a 10-inch grip on a putter shaft of the correct length.
If you want to know the lie for this putter, the angle is the ARCTANGENT of (A/B). This will give you the degrees the shaft will angle off of 90 degrees vertical (minimum of 10 degrees required by the Rules of Golf).
An example is:
LENGTH: 5'5" tall with distance from hands at address to ground of 25" (B) and distance from the spot beneath the hands out to the ball of 8" (A). The SQUAREROOT of (25*25 + 8*8) = 26.25 inches. Add 4 inches. The total length of this putter would be 30.25 inches. The hands will end up halfway down this grip, solidly on the material, and about 1 inch will stick up above the wrist line.
LIE: (A/B) is 8/25, or 0.32. The ARCTANGENT (inverse of Tangent) of 0.32 is 17.75 degrees off vertical. This putter lie, measure from the surface up, is 90 - 17.75, or 72.25 degrees (just a smidgen upright over "standard" 71 degrees or 19 degrees off vertical.
A useful calculator online for this is
HERE.
You should be sure not to get too "perfect" in your setup, but make sure it is a comfortable setup you will actually use daily in golf. Otherwise your measurements will be a little artificial. And remember, it is okay to have a little extra length, so long as the hands don't get off the bottom of the grip material and so long as the top of the putter doesn't hang in your body or clothing. But cutting a putter too short is not easily fixable.
Cheers!
Geoff Mangum
Putting Coach and Theorist
PuttingZone
http://puttingzone.com
Golf's most advanced putting instruction -- you're either in the PuttingZone, or not.
