Pressure Vessel Sizing Calculator

Each head geometry redistributes internal pressure stress differently, so ASME Section VIII gives each one its own thickness formula: hemispherical heads use t = PR/(2SE − 0.2P), 2:1 ellipsoidal heads use t = PD/(2SE − 0.2P), and torispherical (F&D) heads use t = 0.885PL/(SE − 0.1P) with crown radius L ≈ D. The calculator also swaps in a matching volume formula — exact for hemispherical and ellipsoidal, an approximate 0.0847·D³ per head for torispherical — since head shape changes internal volume too.

Joint efficiency E reflects how thoroughly the shell and head welds were inspected — 1.0 for full radiography, down to 0.7 for none — and it sits in the denominator of every thickness formula, so a lower E directly increases the required wall thickness. Dropping E from 1.0 to 0.7 without changing anything else can meaningfully raise both required thickness and estimated weight.

The engine first solves for shell and head thickness from the pressure-stress formulas alone (reported as "calc" thickness), then adds your corrosion allowance on top to produce the "required" thickness shown in the main results. Keeping the two separate lets you see how much of the wall is structural versus how much is corrosion margin.

The weight estimate multiplies total outer surface area (shell plus both heads) by the larger of the shell or head thickness and a steel density of 7850 kg/m³, using one blended thickness rather than separate shell and head weight terms. It's a rough order-of-magnitude figure that ignores nozzles, flanges, supports, and internals, so it shouldn't be used as a fabrication-grade weight takeoff.

No. Design temperature is collected but does not currently feed into the calculation — Allowable Stress is the value the engine uses directly, and it's on you to look that value up for your material at your design temperature from ASME Section II-D (as the field's own helper text says) before entering it.