Angle Cut Calculator

A miter angle is the setting on the saw for an angled cut, measured from a square (0 degree) crosscut. For two pieces meeting at a corner, each piece is cut to half the turn: the saw miter is 180 degrees minus the corner angle, divided by two.

So a square 90 degree corner gives a saw setting of 180 minus 90, over 2, which is 45 degrees — the familiar miter. A tighter corner needs a steeper setting, a more open corner a shallower one.

For example, a 90 degree corner is cut at 45 degrees on each of the two pieces. This calculator gives the saw setting for any corner, frame or single cut, plus the cut geometry on your board.

For a standard square 90 degree corner, you set the saw to 45 degrees and cut each of the two pieces at that angle. The two 45 degree cuts add up to the 90 degree turn, so the joint closes cleanly.

This is the most common miter in trim and framing, which is why 45 degrees is a marked detent on every miter saw. The cut runs at 45 degrees from the edge of the board as well, since the cut angle from the edge is 90 minus the saw setting.

For example, on a 3.5 inch wide board a 45 degree miter gives a long-point to short-point offset of 3.5 inches and a cut face about 4.95 inches long. This calculator works out those figures for your board.

For a closed frame made of equal pieces — a 4-sided frame, a hexagon, an octagon — each joint is mitered to 180 degrees divided by the number of sides. The interior corner angle is 180 times the number of sides minus two, over the number of sides.

So a 4-sided frame is 180 over 4, which is 45 degrees per cut; a hexagon is 30 degrees; an octagon is 22.5 degrees. Every piece gets the same setting on both ends.

For example, a six-sided hexagon frame is cut at 30 degrees per joint, forming 120 degree interior corners. This calculator gives the saw setting and geometry for any frame from 3 to 24 sides.

The corner angle is the angle of the corner itself — the opening where the two pieces meet, measured on the open side. The saw angle, or miter setting, is what you dial into the saw, measured from a square cut. They are related but not the same number.

For a two-piece corner, the saw setting is 180 degrees minus the corner, divided by two. So a 90 degree corner is a 45 degree saw setting, and a 120 degree corner is a 30 degree setting. Reading the corner angle straight off the saw would cut the joint wrong.

This calculator takes the corner angle and returns the saw setting, so you dial in the right number. Enter the corner you measured, not the angle you want on the saw.

Few walls are exactly 90 degrees, so measure the actual corner and let the setting follow. A corner that is a couple of degrees off square needs a saw setting that is half that much off 45 degrees, because each piece takes half the error.

Measure the corner with an angle finder or a bevel gauge and a protractor, then set the saw to 180 minus that corner, divided by two. An 88 degree corner, for instance, needs 46 degrees per piece; a 92 degree corner needs 44.

This calculator takes any corner angle from 1 to 179 degrees and gives the exact saw setting, so an out-of-square corner is no harder than a square one. Always confirm on a test cut.

On a mitered board, the angled cut makes one edge longer than the other: the long point is the tip of the acute corner, the short point is the heel. The long-point to short-point offset is the difference between them along the board, and it equals the board width times the tangent of the saw angle.

It matters for marking and measuring, because a mitered piece is dimensioned to either its long points or its short points, and the offset tells you how much to allow at each end.

For example, a 3.5 inch board cut at 45 degrees has an offset of 3.5 times the tangent of 45, which is 3.5 inches. The cut face itself is the width divided by the cosine of the angle, about 4.95 inches. This calculator reports both.

Most miter saws top out around 45 to 50 degrees, so a very tight corner — which needs a steep setting — can exceed the saw’s range. A 60 degree corner, for instance, needs a 60 degree miter, past what many saws reach.

The usual fix is to cut the complement instead: flip or stand the stock and cut at 90 minus the setting, measured from the other reference, so the blade makes the same cut from the opposite side. A sliding miter saw, a miter jig, or a table saw with a sled are other ways to reach steep angles.

This calculator flags when a setting is past the typical saw range and gives the complementary angle from the edge, so you know the alternative. Always test the setup on scrap first.

A compound miter combines a miter (the saw swung left or right) with a bevel (the blade tilted), and is used for sloped work like crown molding or a tapered box. The flat miter this calculator gives is the miter component with the bevel at zero.

For true compound angles — crown molding sprung at an angle to the wall, or the sides of a canted box — the miter and bevel settings both change and depend on the slope, so they come from compound-miter tables or a dedicated crown calculator.

This calculator covers flat miter cuts with the saw bevel at 0 degrees. For crown molding or sloped sides, use a compound-miter or crown-molding reference for the paired miter and bevel settings.