most of us base the food weight to the snake weight (aka the Munson Feeding Plan). You can find this feeding plan on this site if you take the time to search for it.
It's based roughly on feeding babies 13% to 15% of the snake's weight in food weekly, adolescents 10% to 13% in food every 10 days, and adults once they are full grown just get 1 large mouse every 14 to 21 days.
It's easy to over feed a snake, and snakes can get fat just as any animal can.
A corn snake should not seem fat. Their body shape should not be round (fat) or triangular (too thin) but similar to the shape of a loaf of bread (just right).
Most of us use scales that measure in grams, such as a kitchen scale which can be purchased at walmart, target, or anywhere kitchen wares are sold.
You simply weigh the snake, and then feed appropriately.
Since your snakes are "Adults" weighing them may not be necessary, but you don't want to over feed them. 1 Large mouse (30 to 35 grams) every 14 to 21 days will be fine.
Examples: a baby weighing 20 grams would receive 1 or 2 pinkies totaling 2.4 grams, an adolescent weighing 200 grams would receive 1 mouse weighing about 20 grams, and an adult weighing 500 grams would get 1 mouse weighing about 35 grams.
