Frame moulding calculator
Long point and short point for each pair of rails, from the outside size back to the saw.
Result
Package / glass 16" × 19"
Mat window 10 1/2" × 13 1/2"
Finished outside 18 5/8" × 21 5/8"
Sight opening 15 5/8" × 18 5/8"
Top/bottom long point 18 5/8" · short 15 5/8"
Left/right long point 21 5/8" · short 18 5/8"
Your dimensions will carry over. Add your own artwork next.
- Top/bottom long18 5/8"
- Top/bottom short15 5/8"
- Left/right long21 5/8"
- Face1 1/2"
- Rabbet lip1/4"
- Kerf1/8"
How it works
On a 45° frame the long point equals the finished outside dimension of that side. Opposite rails must match.
The short point is the long point minus twice the face width. Measure the long point on the outside corner, not on the back of the rabbet.
The rabbet is slightly larger than the package so the stack can drop in. The sight opening is what remains after the lip covers the glass.
Common mistakes
- Measuring the long point along the rabbet edge and shrinking the frame by twice the lip.
- Cutting four rails that do not have matching opposite lengths.
- Ignoring saw kerf when those rails later come off one stick.
Frequently asked questions
What is a long point?
The longer mitred edge of a rail. It matches the finished outside dimension of that side.
What is a short point?
The inner mitred edge. For a uniform 45° face it matches the sight opening.
Do I add kerf onto each rail?
No. Kerf is the gap the blade takes between pieces on a stick, not extra length on the rail.