A semicircular arch has the shape of half a circle. Its intrados radius is half the opening width. The brick division and joints determine how the masonry closes at the crown.
Enter the opening, brick size, arch thickness and target joints. Inspect the calculated bricks and connections. The PDF includes the setting-out shape, brick profiles and a 10 cm scale check.
semicircular arch, round arch
Measure the clear width between both springers and choose the brick size and bond. The inner curve is a semicircle, so its rise already follows from half the span.
The centre lies halfway along the springing line. The joint setting-out lines radiate from this point. The outer curve has a larger radius than the inner curve, so the brick and joint widths increase towards the outside.
A 160 cm span gives an inner radius and rise of 80 cm. For a lower arch with the same span, choose a segmental or basket-handle arch.
A free account lets you view the calculation and drawing. The PDF contains calculated dimensions and cutting profiles; a download costs one credit. Follow the scale on the worksheet. Print full-size cutting templates at 100% with ‘fit to page’ disabled.