Frame Size Calculator — Outer Dimensions from Artwork

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.

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.

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.