Quick answer: U.S. pennies stopped being mostly copper in 1982 , when the Mint switched to copper-plated zinc. That change happened during 1982 , so both copper and zinc pennies were made that year.

What changed

Before 1982, modern pennies were made of 95% copper. In 1982, the composition changed to 97.5% zinc with a thin copper coating , which is why 1982 is the key cutoff year.

How to tell the difference

  • Pre-1982 pennies: mostly copper.
  • 1982 pennies: can be either copper or zinc, depending on the exact coin.
  • Post-1982 pennies: copper-plated zinc.

Small collector note

If you’re sorting pennies from change, 1982 is the year to check carefully because it’s the transition year, not a clean before/after line.

If you want, I can also give you a 1-second trick to tell copper pennies from zinc pennies by weight or sound.