Miter Angle Calculator
Calculate miter saw angles for flat trim, or the compound miter + bevel pair for crown molding, from a wall corner angle reading and (for crown) the molding's spring angle.
Input
The reading from a protractor or digital angle finder held against both wall faces at the corner.
Inside corners use (180° − reading) ÷ 2; outside corners use reading ÷ 2 — both agree at a standard 90° corner.
Output
| Property | Value |
|---|---|
| No data yet | |
| Corner | Miter | Bevel |
|---|---|---|
| No data yet | ||
The same saw settings for a few frequently seen corner angles, at your current corner type / trim type / spring angle.
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/miter-angle-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"wallAngle": "90",
"cornerType": "inside",
"cutType": "flat",
"springAngle": "45"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `miter-angle-calculator` tool (Miter Angle Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/miter-angle-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Miter Angle Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
The Miter Angle Calculator turns a wall corner reading into the actual number you dial into a miter saw — a plain miter cut for flat trim (baseboard, casing, chair rail), or the compound miter-and-bevel pair for crown molding cut flat on the saw table, "upside down and backward."
How to use it
- Enter the wall/corner angle — the reading from a protractor or digital angle finder held against both wall faces at the corner. A standard square room corner reads 90°.
- Pick corner type. Inside corners (the normal concave corner of a room) use
(180° − reading) ÷ 2; outside corners (a protruding corner, like a pillar or the outside of a bump-out) usereading ÷ 2. Both agree at a standard 90° corner, which is why most people never notice the difference until a corner is out of square. - Pick trim type — flat trim needs only a miter cut; crown molding needs a compound miter and bevel.
- For crown molding, enter the spring angle — how far the profile leans away from the wall, commonly 38° or 45° (check the molding's packaging or profile spec).
The saw settings appear instantly, along with a reference table showing the same settings for a few commonly seen corner angles.
The math
- Half angle =
(180° − reading) ÷ 2for an inside corner, orreading ÷ 2for an outside corner. - Flat trim: miter = half angle, bevel = 0°.
- Crown molding (cut flat on the table, blade tilted for the bevel, table rotated for the miter):
- Miter =
atan(tan(half angle) × sin(spring angle)) - Bevel =
asin(cos(half angle) × cos(spring angle))
- Miter =
For example, a standard 90° inside corner with 38°-spring crown molding needs a 31.62° miter and a 33.86° bevel — the same numbers as the widely published "38/52" crown molding cutting chart. A 45°-spring crown at the same corner needs a 35.26° miter and a 30° bevel.
Why does corner type matter if the angle reading is the same?
A 90° reading behaves identically either way, which is why most trim carpenters never think about it. It starts to matter once a corner is off-square: a 100°-reading inside corner needs a 40° miter, while a 100°-reading outside corner needs a 50° miter — get the corner type backwards and every joint gapes.
What if I don't know my crown molding's spring angle?
38° and 45° cover the overwhelming majority of pre-primed and stock profiles sold at home centers — try 45° first (it's the more common modern default) and check the fit against a scrap offcut before committing to a full run. Some profiles print the spring angle directly on the packaging.
Do I need to bevel flat trim?
No — a plain miter cut (no blade tilt) is correct for baseboard, casing, and chair rail, since the whole profile lies against a single flat wall. Bevels only come into play for crown molding, which spans the angle between the wall and the ceiling.
For a roof slope rather than a wall corner, use the Roof Pitch Calculator. For measuring or laying out the fence line a piece of trim will follow, see the Fence Calculator.
Everything runs in your browser; no inputs are sent to a server.