How do you pronounce 10x10 I use often measures and dimensions written this way for my job since not a native speaker wonder how spell it?

It's a common way to write down dimensions, especially for things like rooms, furniture, or building materials.

It's pronounced as "by" because it indicates the measurement in two directions. For example, a 10x10 room is ten feet (or meters) wide by ten feet (or meters) long.