Many years ago I found this website, maintained by Lars Josefsson, a person with many years of experience operating boilers, starting up marine steam boiler plants and designing control systems
for marine boilers. I am including this link because I thought some of those visiting my website might find some useful information on Mr. Josefsson's site.
The fifth item up from the bottom of the menu on the left side of his site will take you to a free download of a very comprehensive unit conversion program. I have used this program for many years (ever since the time when it was a DOS program). It includes conversions for just about any category you can think of, 45 of them in all.
Here is a link to Valin Corporation's unit conversion software.
This is nicely done and easy to use. It was developed for Valin by Pipe Flow www.pipeflow.com a company that specializes in
software for pipe network analysis and modeling. (I have no affiliation with Pipe Flow.)