I'm not sure of the dimensions of our coin savings jars - but we have 4 and each one held 40 oz of Snyder's pretzels in them (purchased at BJ's). We have been savings coins for 16 months now. When the one year mark hit, DH and DS12 divided all the coins (which were all in one jar), into the 4 jars, and counted the quarters only. As of last November, there was over $800 in quarters.
We have 5 months to go before our next WDW trip and I'm thinking we will have some decent spending money for our 4 nights, 5 days at the Wilderness Cabins!
I can't believe we haven't done this for years - it's so easy and so worth it.