Cremello + Chestnut = 100% palomino
Palomino + Palomino = 50% palomino, 25% chestnut, 25% cremello
Palomino + Chestnut = 50% palomino, 50% chestnut
By the way, this last combo was originally considered the way to go when producing palominos–that way there wasn’t the risk of getting a cremello. That was back when the double-dilute was not desireable (and also not registerable by the AQHA)