Mount Board Calculator — Mat Board Cutting Dimensions

The standard border width for most artwork is 6-8cm. Larger pieces may suit 8-10cm borders. A wider border gives the artwork room to breathe. A weighted bottom border (2-3cm extra) is traditional and gives a visually balanced mount.

A weighted bottom adds extra width to the bottom border (typically 1-3cm). This is a traditional framing convention that counteracts the optical illusion of the artwork appearing to sink in an equal-border mount. The result looks more balanced to the eye.

The reveal overlap is how much the mount window edge covers the artwork edge. UK framers typically use 4-5mm on each side (a little less for small work, more for large pieces). It hides any uneven artwork edges and stops the artwork dropping through the window opening. The window is therefore cut twice the overlap smaller than the image in each direction.

Order the frame so its inner rebate opening equals the outer mount size plus a small fitting clearance — about 3mm total (1.5mm each side) so the glass, mount and backing drop in without jamming. The rebate lip (roughly 5-6mm wide) then overlaps the mount edge to hold everything in. Do not add the rebate depth to the opening: depth is the front-to-back space for the layers, not a planar measurement.

A 45° bevel cut is standard for picture framing mounts. The bevel reveals a thin white line of the mount board core, creating an elegant transition between the mount and the artwork. Always cut with a sharp blade for clean bevels.