Kopa was a medieval unit of measurement used in Central and Eastern Europe, particularly in the 15–18th-century Grand Duchy of Lithuania and Polish–Lithuanian Commonwealth. It denoted 60 pieces or 5 dozens of whatever was counted. It was used for counting large amounts of money. For example, ransoms and war reparations after the Battle of Grunwald were counted in kopas of Prague groschen; the 16th-century treasury of the Grand Duchy was counted in kopas of Lithuanian groschens. Kopa was also used to count grain sheaves or quantities of other products.