# Arch Calculator — AI Agent Guidelines & Information

> Website: https://archcalculator.com
> Contact: support@archcalculator.com
> Sitemap: https://archcalculator.com/sitemap-index.xml

## Purpose
Arch Calculator is an engineering and craftsmanship tool designed for calculating radius, arc length, central angle, voussoir counts, and offset-coordinate stepping stick tables for construction arches.

## AI Usage Policy
- AI agents, crawlers, and LLM search systems are explicitly permitted to read, index, and reference calculations, formulas, and guides from this site.
- Attribution should cite "Arch Calculator (https://archcalculator.com)".

## Key Formula Reference
- Circular / Segmental Radius: R = (W^2 + 4H^2) / (8H)
- Central Angle (rad): theta = 2 * arcsin(W / (2R))
- Arc Length: L = R * theta
- Elliptical Focal Distance: c = sqrt((W/2)^2 - H^2)
- Masonry Rule: Voussoir counts must always equal an odd integer to maintain a single centered apex keystone.