Carpentry and Woodworking - Mitre measurments

I have a decorative trim that I need to put around the top of a bedroom wardrobe and bookcase that sits in the bedroom. One unit has a 90° corner and one has two 45° corners. I am wondering if there is some kind of chart or formula that will tell me how to measure so I make the cuts the right length.

The trim is 1 and 1/8 inch thick and 4 inches tall.

Thank you.

hi
i would invest in a miter box.
there not expensise and some come withy backsaw included.

Measure the length that needs the trim and then cut that measurement to the inside of the mitre. If in doubt cut long, fit, re measure and cut again.

When I'm cutting trim, I'll measure the short point to short point, add any reveal (if putting up casing) and add 2x the thickness of the trim. Then when I cut, I'll measure from long point to long point- since it's almost impossible to measure short point to short point accurately.

Example: Putting up 2 1/4" wide casing. The head piece of casing goes on a jamb that is 32" wide (inside to inside) I want to have 1/8" reveal on each side, so that gives me 32 1/4". Since I measure from long point to long point when I go to cut the trim to length, I'll add 2 1/4 + 2 1/4, which would be 36 3/4. I always cut my left miters all first, so that when I hook my tape on that long corner and pull my measurements, it's always from the same side.

So if your trim is getting installed around the outside of the wardrobe, then measure the length by measuring a side of the wardrobe (outside to outside on the wardrobe, but short point to short point on your trim), and if that piece will have two 45 degree outside corners, you would take your measurement and add 1 1/8 + 1 1/8 to get an outside to outside measurement (long point to long point on your trim).

If you have a miter box now ? I always use short point measurement for any thing I cut in a miter box you can do this buy cutting the first cut one end of your trim and using a long board lay your trim down on the board and set the short point cut even with the end of that board make sure its even and that will allow you to pull your measurement from the end of that board that your trim is on thus not moving your trim peace when you measure and you need to keep the peace of trim out close to the edge of the board so you can hit the side of your trim with the measuring tape to make your next short point mark.
this short point technic is good for outside corners. For inside corners make that first cut and flip your trim over and pull your tape down the back side ( near the edge) and mark your second cut.
If you cut crown moulding you have to place you trim into the miter box upside down which means that you will be cutting the left side in the box but it will be the right side when you appy it to the wall. this means that you are cutting it upside down and backwards if that makes since. hope this didn't make you confused . post back if you need more confusion.