What Is the Arch Calculator?
Calculate arch dimensions including radius, rise (height), span, arc length, and segment area for arched openings, doorways, and decorative stair features. Arches are used in stair halls, entryways, and over landings to create elegant architectural details.
How to Use This Calculator
- Enter the span (width) of the arch and the rise (height from springline to crown).
- Review the calculated radius, arc length, angle, and segment area.
- Use the radius for layout on plywood templates or flexible trim.
Why Accurate Arch Calculations Matter
Arch geometry determines the structural behavior and material requirements. A segmental arch (less than a semicircle) has different thrust forces than a full semicircular arch. Accurate radius calculation is essential for ordering pre-bent trim, flexible molding, or CNC-cut plywood arch forms.
Building Code References
Related Tools
Frequently Asked Questions
How do I calculate the radius of an arch?+
For a segmental arch: Radius = (Span²/4 + Rise²) / (2 × Rise). For a semicircular arch, the radius simply equals half the span.