Why Penny Count by Weight Won’t Work

Counting pennies by how many pennies per pound just does not work. But why? That’s because not all pennies weight the same. In 1982, the metal composition of the penny was changed from being made of 95% copper to 97.5% zinc. This mean the weight of each penny changed from 3.11 grams to 2.5 grams.

The grams weight of a penny being off by simple fractions may not seem like much, but there are 1,000 pennies in $10 face value, 5,000 in a $50 bank penny bag. When you weight a $50 bag of pennies made entirely of zinc, the weight will come to approximately 27.5 pounds. A bank bag of copper pennies totaling $50 face value weighs approximately 34 pounds.

So 34 pounds of copper pennies - 27.5 pounds of zinc pennies equals a potential difference of 6.5 pounds! That’s a huge difference in terms of pennies per pounds. 6.5 pounds of zinc pennies is approximately 1,179 pennies, or $11.79 in face value. 6.5 pounds of copper pennies is approximately 948 pennies, or $9.48 in face value. That means there could easily be a $2.31 difference, or a miscount of 231 pennies.

Next time someone tells you to save time counting pennies by just putting them on a scale, remember that depending on which material the penny is made of, copper or zinc, the actual weight-to-count may just not be so accurate.

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