How to cut molding inside corners
Inside corners can be mitered, coped, or built from purpose-made blocks. The best method depends on molding profile, movement, visibility, skill, and whether the corner is actually square.
Compare mitering, coping, and corner blocks.
A two-piece miter is fast and symmetrical when the walls are stable and the profile can be registered consistently. A coped joint leaves one piece square into the corner and shapes the second to follow its face, hiding some movement and angle error. A corner block removes the profile intersection but changes the design.
Choose before measuring lengths because each method uses different long points and sequence. Keep a labeled sample of the molding profile to confirm orientation at every corner.
Use the actual installed spring and reference faces.
Measure the corner where the molding contacts the wall or ceiling. Baseboard often references table and fence directly; crown may be nested at its installed spring angle or cut flat with compound settings. Do not assume the decorative face provides a stable reference.
Mark wall side, ceiling or floor side, top, bottom, left, right, and waste. Build safe support blocks only where the saw and molding manufacturer permit them, and verify the disconnected motion envelope.
Make the reference piece first, then fit its mate.
For a coped joint, install or test the square-cut reference piece, cut the mating profile to reveal its contour, and remove waste with an appropriate coping tool while staying just outside the line. Back-bevel as needed so only the visible edge contacts.
For a mitered pair, cut both labeled scraps at the calculated starting settings and fit them together. Use a fine, suitable blade and full material support; never hold a short profiled return beside the blade.
Correct the wood joint before fastening it to the wall.
Test the pieces at their installed angle and inspect the visible profile from normal viewing height. Relieve unseen back material carefully rather than crushing a decorative edge. A coped face should contact cleanly without a large hollow that weakens it.
If the wall corner itself is damaged or rounded, decide whether surface preparation, scribing, caulk, or a different joint is appropriate. Fasteners should secure a fitted joint, not pull a poor miter into alignment.
Questions readers ask before they start
Is coping better than mitering inside corners?
Coping often handles profiled trim and small wall-angle changes better, while mitering can be efficient for stable, simple profiles.
Are inside corners always 45-degree cuts?
No. Two 45-degree miters fit an exact 90-degree corner only. Measure the actual included angle.
Can crown molding be cut flat?
Many saws support flat compound-cut tables for specific spring angles. Follow the exact manual and molding geometry.
Check the exact saw manual before changing or adjusting anything.
The geometry is explained in plain language and the operating steps are checked against OSHA guidance and current manufacturer manuals. Your exact saw manual controls setup and capacity.