Arch Calculator

An elliptical arch is a curved architectural structure based on an ellipse shape. Unlike circular arches, elliptical arches have two focal points and can have different width-to-height ratios, making them more versatile for various design applications.

To measure an elliptical arch, you need the height (H) from the base to the highest point and the width (K) which is the total span at the base. These two measurements are sufficient to calculate all other arch parameters including focal distance and radius.

The focal distance (G) is the distance from the center of the arch to each focal point. These focal points are used when drawing the elliptical arch with string and pins, ensuring the arch maintains its proper elliptical shape throughout construction.

Not necessarily. While some arches are semicircular, elliptical arches are based on half of an ellipse, not a circle. The shape depends on the ratio between height and width - when height equals half the width, it becomes a perfect semicircle.

To draw an elliptical arch, mark the focal points at the calculated distance from center, tie a string between them with total length equal to the major axis, then trace the curve while keeping the string taut. This creates a perfect elliptical shape.

The arch radius is the radius of curvature at the top of the arch, while focal distance is the distance from center to the focal points used for construction. The focal distance is always less than the semi-major axis of the ellipse.

Yes, the arch height can be greater than half the width, creating a tall, narrow elliptical arch. However, when height equals exactly half the width, the result is a perfect semicircle rather than an ellipse.

Eccentricity measures how much the elliptical arch deviates from being circular. An eccentricity of 0 means a perfect circle, while values closer to 1 indicate a more elongated ellipse. Most architectural arches have eccentricity between 0.3 and 0.8.