16. Or an integer multiple of that like 32 or 64. It's in the Step 5: Exporting section Edit: that's the height, the width is not fixed/I think it varies with

16. Or an integer multiple of that like 32 or 64. It's in the Step 5: Exporting section Edit: that's the height, the width is not fixed/I think it varies with the exact font and the kerning. It's probably too big for you anyways.