Spark plug thread size

1

I am wondering the thread size of the plugs. I think it must be a hair under 7/8”.

2

For a stock head, the spark plug size is 1/2 inch pipe thread.

3

Thanks. I need a little education on pipes and threads. So the size of the pipe is determined by the inside measurement which makes sense. My old plug seems to allow a die to thread loosely with 7/8” and 14 threads per inch. I have a 3/4” but the number of threads is16 per inch which seems to be too many. It probably should be 14 as well. I will take it over to a neighbour to see what dies he has.