The aim of this study was to produce design charts to predict inelastic collapse pressures for thick-walled circular cylinders under uniform external pressure because the existing charts were out of the range for shorter and thicker vessels. Both theoretical and experimental investigations were carried out on 15 stainless steel models, which were tested to destruction and reported for the first time. A theoretical investigation was also carried on other models, tested by previous researchers, to give more points and more credibility to the design chart.