Mat and frame size calculator
A frame shop asks for three numbers: the sheet, the mat border and the moulding width. The calculator adds them so the window matches the art and the frame is not smaller than the mat.
Calculator form
How to use
Measure the artwork
Width and height of the sheet or canvas, without an old frame.
Set the border and the moulding
The border is the card on each side. The moulding is the face width of the frame.
Order the outside size
The shop cuts the frame to the outside measurement. The mat window equals the artwork.
Sample calculations
30×40 cm, 5 cm mat, 2 cm moulding
Mat outside 40×50 cm. Frame 44×54 cm
Common mistakes
Mistake
Adding the border to one side only → The border sits on both sides, so the addition is doubled.
FAQ
What if the window should overlap the sheet?
This result makes the window equal to the sheet. For a 2–3 mm overlap per side, shrink the window yourself.
Is moulding the face width?
Yes, the strip you see from the front. The rabbet depth does not change the window size.
Lock it in with practice
Open the free editor and apply the result — a short sketch beats more reading.