Arch Design Guide
Arches are circles cut down to the width of your opening — the math is simple once you see it that way.
Understand the Arch
An arch spans an opening with a curved top that is part of a circle. The key questions are the opening width and the rise you want.
Radius and Arc Length
Radius (R) = (w² ÷ 8h) + (h ÷ 2)Where w is the opening width and h is the rise (height) of the arch at its crown. The arc length is then the curve of that circle inside the span.
Count the Bricks
Bricks in the arch follow the curve, so they are laid radially. Estimate using the same per-square-foot method as a wall, but account for the radial joints slicing the bricks.
Solid Angle Consideration
If you are building a half-round (semicircular) arch the angle is fixed at 180°. A segmental arch has a smaller central angle — the arch calculator finds it from your rise and width.
Related Calculators
Disclaimer: Figures on this page are general reference information. Always verify exact requirements with your project specifications and a qualified professional.