Approximately 5,000 pennies fit in a gallon jar, totalling approximately $50. The number of pennies that will fit in a jar may vary, though, based on the position of each penny in the jar.
The thrifty saver can also estimate the number of pennies in a gallon jar by weighing the contents. For example, weigh the empty gallon jar first and then fill with pennies. Estimating that each penny weighs 2.5 grams, the saver can weigh the jar full of pennies, subtract the weight of the empty jar and divide the remaining weight in grams by 2.5 to identify the number of pennies in the jar.