What I use when drawing a 21' diameter stack out of 1/4" plate is 3.14. same for coming up with the length to order and cut before rolling it.
Close enough lol. Of course I'm a dinosaur. I still use a trig foot and inch calculator as does most other people in my line of work. They may draw it on a computer but everything is checked with a calculator or the same app on a phone, but the caculator battery last forever and ever and easier to read and easier to replace if you drop it off the top of said smokestack at some point. Every bridge, building, structure, chemical plant, refinery, overpass etc.. done on a calculator. Stop making stuff hard