Bolts are specified by the thread diameter and thread pitch. You do not have a 36 mm bolt in a car.
Making reference to the size of the hex head of the bolt has nothing to do with the bolt size. Maybe you simply need a 36 mm hex socket or wrench to loosen/tighten/hold the bolt.
To buy a socket or wrench, you buy a 36 mm socket or wrench.
Now, regarding your actual question. There are 25.4 mm per inch. So,
36 ÷ 25.4 = 1.417 inches.
If you want to buy the closest equivalent English size, it's 1⁷/₁₆", which is 1.437 inches.
On a tape measure that shows 16ths of an inch divisions, 36 mm is between
1³/₈" and 1⁷/₁₆"
A 36 mm wrench would fit fairly well on a 1³/₈" hex. I don't know of any American bolt with that size hex head, but my old house has some plumbing fittings that require a 1³/₈" wrench or socket.
I'm not sure what you're trying to do.
-Engine overhaul mechanic and general automotive mechanic since 1972. Retired in 2018.