Second fix
Architrave: three-sided long points
- where
- leg long point (mm)
- opening height (mm)
- reveal (mm)
- trim face width (mm)
- head long point (mm)
- opening width (mm)
Explain this equation
Gives the long-point lengths of architrave for a square, mitred door or window surround: two legs and a head.
H and W are the opening height and width in millimetres. r is the reveal, the step back from the lining edge. t is the face width of the architrave. lleg and lhead are the long-point lengths, measured on the outer edge of each mitre. The calculator also totals the cut length for one or two faces.
Each leg runs the opening height, plus the reveal, plus the head's width where it meets the mitre. The head spans the opening plus a reveal and a trim width on each side, hence the 2(r + t). The 45° mitres make the long point exactly one trim width beyond the inner line.
An 838 × 1981 mm opening with a 5 mm reveal and 70 mm architrave gives 2056 mm legs and a 988 mm head. Both sides take about 10.2 m.
Watch out: this assumes a square frame, 45° mitres and equal trim widths. Out-of-square openings need marking off in place.
Calculate two legs and a head for a square, mitred frame with equal-width architrave.
Enter your values to see the result.
Good to know
Measured from floor/base to opening head and across opening. Assumes 45° mitres, equal trim width and square frame. Scribed or unequal-width details need their own layout.
Sources
- Geometry / arithmetic
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.