These are the directions I'm using:
Measure Your Horse's Girth
I used a piece of haybale twine to measure JT today, and then brought it home to measure with a yardstick. It's 68" long, so 68 divided by 2 is 34, and 34-3 is 31. I'm not sure if I should get a 30" cinch or a 32" cinch. I'm leaning toward 32" inch because that would give him room to add a little more weight, or for wintertime when he's got the fuzzies.