Math formula to lay out bevel angle

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Hello.  I've been struggling with this for a while... Never been able to figure it out. No help online...  I know there is a way just not sure how...So given a specific wall thickness how far back do you have to measure, then wrap and grind to set line to get a specific bevel angle? Example: 1/2" wall... Measure 1/2" back (on square pipe) to get a 45 degree bevel... What about 37.5? 30? 5/8 wall... Etc etc... Yes I know there are gauges, eye it... But I want a good starting point for random pipe sizes.  I know there is a formula where you can plug in wall thickness, then the bevel angle and get a measurement on how far back to measure to get said angle....Just not sure what it is...
Reply:Depends which way you want to define the bevel.  It's basic trigonometry. Attached.-DaveXMT304 with: 22A Feeder, or HF251 Hi Freq DC TIG air cooled
Reply:Forget about it. Nobody does it that way. Cut yourself a gauge out of a scrap piece of sheet metal. Get used to standing and holding your grinder or torch the same way. Grind 1/2" of bevel, check with the gauge and adjust. Then hold the same angle as you go. Keep checking and adjusting. Keep doing it and eventually it becomes muscle memory and you don't need the gauge.