Crown Moulding Calculators

Sources for charts and calculators that provide compound-cut angles for crown moulding installation. February 8, 2008

I'm putting up some crown on a tray ceiling. The split angle on a flat molding where the pitch meets the horizontal is 13 degrees. Is there a way of calculating or rules for cutting the crown other than trial and error? My feeble brain tends to lock up when the third dimension is added. I'm not called upon to do this much, and would greatly appreciate any tricks, condolences, or admonitions you experts may have.

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor S:
I am not quite sure that I understand. The crown is running along a wall and then angles up into the treyed area? Or the crown is being bedded between an out of plumb wall and a horizontal lid?

From contributor E:
Find a good disguise, sneak into a local Lowe's or Home Depot and go to the crown molding row. They have a Blue & White crown molding installation book that is a bible. It's about $18 and has techniques for all angles and ceiling pitches and good photos for regular and compound miter boxes. Sorry I don't have the book here for the exact name, but it's put out by the maker of the transparent angle finders that they sell alongside the moldings. It's worth every penny.

From contributor O:
I believe the book contributor S is thinking of is called "Crown Molding and Trim." The web address is, offered by the Quint Group Company. The transparent angle finders are called True Angle.

From the original questioner:
Thanks gentlemen. Now my only problem is figuring out what disguise to wear.

From contributor K:
Go to and download their calculator. It has lots of tips and techniques for all sorts of angle questions. I think it costs less than $20 and you don't need a disguise. You could even download it in your undies.