Picture Frame Cut Lengths: Long Point, Short Point and Kerf

For a rectangular picture frame with uniform moulding and 45° mitres, each rail’s long point equals that side’s finished outside dimension. Its short point is the long point minus twice the face width. Kerf consumes stock between pieces; it does not enlarge the finished rails.

The top and bottom form one matching pair, and the left and right form the other. These are photo-frame lengths, not room-trim measurements.

Six terms that must not be swapped

Long point

The outer-corner-to-outer-corner length of a finished rail. This matches the outside frame width or height in this rectangular model.

Short point

The shorter front inner edge between the mitres. It matches the sight opening for a uniform face, not the back rabbet recess.

Moulding face width

The width visible from the front, measured across one rail. For 45° ends, the two corners account for twice this width between long and short points.

Rabbet overlap

The lip width covering the package edge. Rabbet depth is a different measurement, used for stack thickness.

Fitting clearance

The space around the mat, glass and backing. FramingLab’s field is per side; two sides increase each recess dimension.

Kerf and purchase length

Kerf is material removed by the blade. Purchase length is the usable stick length needed for your cutting process, including losses and allowances, rather than just the frame’s perimeter.

Stock allowance is additional length reserved per rail in the cutting plan. It is separate from fitting clearance and kerf; choose it for your own trimming process rather than changing the finished frame dimensions.

What the stock model does—and what it leaves out

The finished rails total 80 1/2". In the length-packing example, four pieces share three between-piece gaps of 1/8", giving a modeled used length of 80 7/8" on one new 96" stick.

That is a model result, not proof that three saw cuts make a frame. Four rails have eight mitred ends. The optimizer does not reserve every initial trim, angled offcut, damaged section or saw-specific sequence. Do not buy exactly the modeled used length and assume it covers all these losses. Verify the usable stick length and add the allowance your process needs.

Workshop packs profiles separately and labels unrecorded new stock as Purchase required. Ordinary projects start with no owned inventory. Recording stock or downloading a plan does not confirm that cutting happened; inventory updates use the separate confirmation action.

At the saw

Logan’s F100-2 manufacturer manual, pages 3–4 describes setting the fence and stops, supporting and clamping the moulding, and using its rabbet-corner reference. Follow the instructions for your own saw. Its scale may expect a back-recess measurement rather than the long point listed here.

In this engine, outside = package + 2 × clearance − 2 × lip overlap + 2 × face. If a manual uses a different definition of inside length or moulding width, translate the reference first. Do not add fitting clearance a second time to a rail already calculated with it.

Common mistakes

• Cutting a rail to the matboard size instead of the appropriate long, short or rabbet reference.
• Adding kerf to each finished rail or assuming a zero-waste packing guarantees a physical cut sequence.
• Mixing different profiles because their lengths happen to fit together.
• Forgetting to regenerate the rails after changing the window, borders, face width or clearance.

Use the corresponding tools

Calculate all four picture-frame rail lengths

Compare long points, short points and the rabbet, or continue the example in Studio and choose Workshop for stock planning. Check opening versus outside size before translating a retail specification.