Volok (Lithuanian: valakas, Polish: włóka, Belarusian: валока, Russian: волока) was a late medieval unit of land measurement in the Grand Duchy of Lithuania, Kingdom of Poland and later, the Polish–Lithuanian Commonwealth.
[2] Previously, taxes and duties were based on the number of households (see, for example, 1528 census of the Grand Duchy of Lithuania that recorded households as a measure of military duty) or number of horses/bulls needed to work the land.
Such system was not exact: households varied greatly in size and in wealth.
Therefore, the introduction of voloks marked an important transition to taxes based on area (width times length).
Officially, voloks were abandoned as a unit after the emancipation reform of 1861, but survived in everyday use until the introduction of the metric system in 1921.