Building a custom Firepit grill/grate for friend

[cubangt]

i going to see about sticking with 1/4" round and 1/4" grate, something simple, but reinforced under the grate with their family initials. Still working on the design.....

[cubangt]

So need some advice on what or how i can do this.. I have the material and design idea for it.. but what im having a hard time calculating is the length of round rod i need in order to make a 28" round trim for the grate.

He has a fire pit in his backyard.. which right now he uses...