I try to look at the ears of the deer. I've always been told that the average deer's ear is 6" long and the spread from ear to ear is about 15".

When someone asks the estimated score on the deer I think compare the ear length with the tines and go from there. I have a 10 key calculator sitting on my desk and I just add up the tine length on it. I then make a guess on the main beam lengths and spread and lastly I look at the mass of the antlers. That's where I give it my biggest swag. I use 20" as a base number for a medium mass deer. Deer with light mass drop down from there and heavy mass goes up from there. I usually compare the size of the deers ear with the base of the antler to help on this as well.

On the deer you posted a picture of I estimated the score as follows:

Left - G1 - 5, G2 - 9, G3 - 6, main beam 20
Right - G1 - 5, G2 - 10, G3 - 9, G4 - 5, main beam 20
I guessed the inside width at 18 and to me it had medium mass so I gave it 20" circumference measurements for each side.

That comes to 147" gross and it would lose 9" off that to come to a net of around 136".

I didn't try to match your posted score with those number, that is just comparing the ear to the tines and going from there. The main beams and spread are just guesses but you can usually get a pretty good idea based on the other tines.

That's how I do it. I usually get pretty close if they go back and post the score later.