Compound Miter Calculator for Construction Cuts

Calculator inputs

Use one unit system throughout the form. The cost field should match the same chosen length unit.

Corner type

Cut hand

Length unit label

Currency symbol

Example: $, €, £, Rs

Corner angle (degrees)

Spring angle (degrees)

Molding face width

Piece run length

Straight installed run before the corner addition.

Stock thickness

Available stock length

Saw kerf

Extra allowance

Use for coping margin, sanding, or field trimming.

Quantity

Waste percentage

Unit cost per length

Plotly graph

This chart shows how miter and bevel settings change as the corner angle changes while keeping the current spring angle fixed.

Example data table

Sample values below use meters and show the resulting saw settings and purchasing estimate.

Corner type	Hand	Corner angle	Spring angle	Face width	Run length	Quantity	Miter	Bevel	Stock pieces	Purchase cost
Interior	Left	90.00°	38.00°	0.120 m	2.400 m	6	42.1468°	33.8629°	6	$157.50

Example takeaway: With a 90° corner and 38° spring angle, the cut needs about 42.15° miter and 33.86° bevel.

Formula used

These formulas are for a flat-table compound cut, often used for crown and similar trim profiles.

Half corner angle = C / 2

Miter = atan( sin(C / 2) / tan(S) )

Bevel = asin( cos(C / 2) × cos(S) )

Ceiling projection = Face width × cos(S)

Wall drop = Face width × sin(S)

Ceiling edge offset = Ceiling projection × tan(C / 2)

Wall edge offset = Wall drop × tan(C / 2)

Suggested cut length = Run length + dominant offset + allowance + kerf

Reserved total length = Suggested cut length × quantity × (1 + waste%)

Stock pieces to buy = ceil( Reserved total length / stock length )

C is the included corner angle in degrees, and S is the spring angle in degrees. Trigonometric functions are converted internally before calculation.

How to use this calculator

Choose whether the cut is for an interior or exterior corner and select the hand of the current piece.
Enter the included corner angle and the installed spring angle of the molding or trim.
Add face width, thickness, stock length, run length, kerf, and any extra field allowance.
Set quantity, waste percentage, and cost per chosen length unit.
Press calculate to place the result block above the form, review angles, stock demand, chart trends, and download files.

FAQs

1) What is a compound miter cut?

It combines a miter setting and a bevel setting in one cut. Carpenters use it when trim meets corners while leaning at a spring angle, such as crown, casing transitions, and sloped frames.

2) Which spring angle should I enter?

Use the installed spring angle of the molding profile. Common values include 38°, 45°, and 52°. Measure the angle formed between the trim back and the wall or ceiling before entering it.

3) Do inside and outside corners use different formulas?

The angle magnitudes stay the same for the same corner and spring angles. What changes is cut orientation, handedness, and which edge becomes the visible long point after installation.

4) Why does the calculator ask for kerf?

Kerf is the material removed by the blade. Including it improves stock planning, especially when many repeated cuts are needed and small losses can accumulate into a noticeable shortage.

5) Why can the stock piece count seem high?

Waste allowance, kerf, long-point additions, and buying full stock lengths all increase the count. The tool estimates what you need to purchase, not just the perfect theoretical cut total.

6) Can I use metric or imperial units?

Yes. Keep every length field in the same unit system from start to finish. Your cost input should also match that same chosen length unit for a consistent estimate.

7) Why is stock thickness included?

Thickness helps estimate section area and rough trim volume. It also gives a better material record when comparing different profiles, suppliers, or job packages during planning and ordering.

8) Can I use this for nested crown cutting?

No. These equations are for flat-table compound cutting. Nested crown setups use different saw relationships, so confirm your cutting method before applying the values on site.