Arch Calculator: Determine Arch Span, Rise, Radius, and Arc Length

Calculate Arch Dimensions Instantly

The horizontal distance between arch supports.
The vertical distance from the spring line to the arch's highest point.
Select the unit for your inputs and results.

Use our free online Arch Calculator to quickly determine key dimensions of a circular arch like its span, rise, radius, and arc length. Essential for architectural design, construction, and DIY projects, ensuring accuracy and saving time on complex calculations.

Formula:

For a circular arch, given the Span (S) and Rise (H):

  • Radius (R): R = (S² + 4H²) / (8H)
  • Central Angle (α in radians): α = 2 × arcsin(S / (2R))
  • Arc Length (L): L = R × α

Where:

  • Span (S): The horizontal distance between the arch supports.
  • Rise (H): The vertical distance from the spring line (line connecting supports) to the highest point of the arch.
  • Radius (R): The radius of the circular arc.
  • Arc Length (L): The total length of the curved arch itself.

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