Pressure Vessel Design Calculator

This calculator applies the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 formula for a cylindrical shell under internal pressure: t = PR / (SE − 0.6P), where P is the design pressure, R the inner radius, S the material's allowable stress, and E the weld joint efficiency (1.0 for full radiography, 0.85 for spot, 0.70 for none) — this is the code's own equation for the required minimum shell thickness, not a textbook simplification of it. That minimum thickness is a bare theoretical number; the calculator adds your specified corrosion allowance on top to get a design thickness, then rounds up to the nearest standard plate gauge from a built-in list (3/16" through 2") since mills don't roll arbitrary thicknesses. It then works backward from that selected plate — subtracting the corrosion allowance to get the actual load-bearing thickness — to recompute the real hoop (circumferential) stress the vessel will see in service, using the fuller ASME form P(R + 0.6t)/(tE) rather than the simplified thin-wall P·R/t, which matters more as the R/t ratio gets smaller.

Longitudinal stress is reported too, but this calculator derives it from the plain thin-wall form P·R/(2tE) rather than the same thick-wall correction used for hoop stress, so the two figures won't land in an exact 2:1 ratio here — longitudinal comes in a bit below half of hoop, and the gap widens as the shell gets thicker relative to its radius. The textbook relationship still holds approximately and remains the reason pressurized cylinders split lengthwise, not around their circumference, when they fail. Two things trip people up: this formula is only valid for the thin-wall regime the ASME rules assume, and the allowable stress input must already reflect your material and design temperature from ASME Section II — the calculator has no material database and takes whatever number you give it at face value.