What is moulding width?

Moulding width is the face width of the frame profile — how much frame you see from the front. Common widths range from 20 mm for slim modern frames to 80+ mm for ornate gallery frames.

What is a rebate, and how is depth different from overlap?

The rebate (or rabbet) is the L-shaped step cut into the back of the moulding that holds the glass, artwork and backing. Two separate measurements matter. Rebate DEPTH is how far back the step is cut (typically 10-12 mm) and governs how many layers — glass, mount, art, backing — will physically fit. Rebate OVERLAP (the lip width, the input on this page) is how far the front edge of the moulding sits over the face of the artwork, hiding the outer edge from view. UK mouldings typically overlap 5-7 mm per side (around 6 mm, the ¼-inch standard lip), so the default subtracts roughly 12 mm total from the visible width and height.

How much bigger is a frame than the artwork?

The outer frame is larger by twice the moulding width in each direction. A 400 × 300 mm artwork with 30 mm moulding produces a 460 × 360 mm outer frame size.

ArtCalcs

Frame Size Calculator — Outer Dimensions from Artwork

Calculate the outer frame dimensions based on artwork size and moulding width.

Artwork Width

Measure the artwork itself, edge to edge — the piece you are framing, not any existing mount

Artwork Height

Height of the artwork edge to edge; for a stretched canvas measure the visible front face

Moulding Width

Face width of the frame profile

Rebate Overlap

Lip width — how far the moulding sits over the art face per side (UK norm 5-7 mm; ¼-inch ≈ 6 mm)

How We Calculate This

Outer frame = Artwork size + (2 × Moulding width)

The rebate opening adds the clearance (default 3 mm total, 1.5 mm each side) to the artwork size so the piece drops in with a small fit gap. The visible area is the artwork minus twice the rebate overlap, because the moulding lip covers the art edge on both sides of each dimension.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.