"Stone" is the fictional unit used for the weight of everything in Life is Feudal. Weight is taken into calculations during combat, but mostly used to measure the amount of items that can be carried around by characters or stored in various containers.
One Stone can be roughly imagined as one kilogram, or 2.2 pounds. Every container has a weight limit in stones. So you can't fit a lot of items if the sum of their weights is higher than the weight capacity of that container. ~ Bobik
(Stone is not to be confused with the crafting material rock.)