I have measured briefly. The seat surface on the wood is 47 cm x 40 cm. If the cushion is wider than 40 cm, you lose about 3 cm of the 47 cm at the back because of the backrest. On each side you have an additional 5 cm to the armrest. So you could take a 50 cm wide cushion instead of just 40.

Great, thank you very much for measuring! Are you satisfied with the quality? Do you have the chairs in a set with the table? LG