Ordered a double glaze unit give the guy the size in inches and he converted it in to metric when i picked it up it was wrong size he said his fault and would order another one week after went to pick it up an now he saying my fault and i have to pay again
Iy may depend where the problem occurred.
Were your imperial measurements definitely correct? If he can show you gave the wrong figure but he converted your figure correctly then I think he could expect payment.
But if your figure is correct and he miscalculated the conversion or he made the wrong size then it's his problem.