Arch Calculator

Design and calculate measurements for elliptical and segmental arches with precision.

Arch Dimensions

Units

Span (Width) (in)

Rise (Height) (in)

Arch Specifications

Designing an archway?

Enter the span and rise of your arch to determine the radius and arc length needed for construction layout.

Overview

A segmental arch is a part of a circle. Calculating its exact radius and arc length is essential for creating templates, building forms for masonry, or cutting wood headers. This tool uses the chord and sagitta (rise) properties of a circle to solve for the missing dimensions.

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Pro Tips

Use the Arc Radius to create a compass with a string and pencil to draw the arch template on your material.
The arc length tells you exactly how much material (like flexible trim or custom masonry) you need for the curved face.
In structural engineering, the rise should ideally be at least 1/8th of the span for stability.

Fun Facts

"The Romans were the first to extensively use the arch in architecture, allowing them to build massive aqueducts and bridges."
"The 'keystone' is the stone at the very top of the arch that locks all other stones into place."
"A 'true' arch supports weight through compression, pushing the load outwards and downwards."

Formula: Radius = (Rise / 2) + (Span² / (8 × Rise)); Arc Length = Radius × θ (in radians)

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