What border width should I use?

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.

What is a weighted bottom border?

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.

What is the reveal overlap?

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.

What frame size do I order for this mount?

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.

What angle should the mount be cut at?

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.

ArtCalcs

Mount Board Calculator — Mat Board Cutting Dimensions

Calculate mount board outer dimensions, window cut size, backing board and frame size for picture framing.

Artwork Width

Visible image size to be matted

Artwork Height

Visible image size to be matted

Mount StyleEqual borders, or weighted (extra at bottom) for traditional balance

Border Width

Width of mount on each side (typically 6-8cm)

Rebate Clearance

Total fitting gap added to mount size for the frame opening (~3mm = 1.5mm each side)

How We Calculate This

Calculation Method

Window cut = Artwork size − (Overlap × 2) on each dimension
Outer mount = Window + Border on each side (+ bottom extra if weighted)
Backing board = Same as outer mount dimensions
Frame size = Outer mount + Rebate clearance (~3mm total), the inner opening you order the frame to

Frequently Asked Questions

Related Calculators

Frame Size Calculator

Calculate outer frame dimensions based on artwork size and moulding width. Includes rebate allowance and overall measurements.

Mat Board Calculator

Work out mat board dimensions and opening size with correct border widths. Includes weighted bottom border for professional results.

Glass Size Calculator

Calculate the glass or acrylic glazing size needed for your picture frame. Covers standard glass, non-reflective and UV-filtering.

Frame Moulding Calculator

Calculate the total length of frame moulding needed including mitre joint waste allowance. Free online calculator for framers.

Backing Board Calculator

Work out backing board dimensions and material needed for your picture frame. Covers MDF, foam core, corrugated board and acid-free options.

Last updated: June 2026

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