Rolling Offset Calculator

The Rolling Offset Calculator is a specialized tool for plumbers, pipefitters, and electricians who need to calculate the precise length and angles for a "rolling offset." A rolling offset occurs when a pipe or conduit needs to change direction both horizontally and vertically simultaneously to navigate around an obstruction.

What is a Rolling Offset?

Imagine a pipe running along a wall that needs to connect to a point that is not only higher but also further away from the wall. Instead of using multiple 90-degree fittings to make two separate turns, a rolling offset uses two angled fittings (commonly 45° or 22.5°) to create a single, diagonal "rolling" run that changes plane in two directions at once. This results in a cleaner installation and better flow characteristics.

How to Use the Calculator

The calculator requires three key measurements that form a right-angled triangle in 3D space:

1. Rise (Vertical Offset): This is the vertical distance the pipe needs to travel up or down.
2. Advance (Horizontal Offset): This is the horizontal distance the pipe needs to travel forward, parallel to its original path.
3. Offset: This is the horizontal distance the pipe needs to move sideways, perpendicular to its original path.

After entering these values, the calculator provides the two most critical pieces of information for fabrication:

• True Offset (or Travel): This is the actual end-to-end length of the diagonal pipe piece needed to connect the two points.
• Angle of Roll: This is the angle at which the fittings must be rotated or "rolled" to achieve the correct alignment.

The Math Behind the Rolling Offset

The calculations are based on the Pythagorean theorem, but applied in three dimensions.

Calculating the True Offset (Travel)

The true offset is the hypotenuse of a 3D right triangle. Its length is found by calculating the square root of the sum of the squares of the rise, advance, and offset.

True Offset (Travel) = √(Rise² + Advance² + Offset²)

This gives you the exact length to cut your diagonal piece of pipe.

Calculating the Angle of Roll

The angle of roll is determined by the relationship between the Rise and the Offset. It's found using trigonometry, specifically the arctangent function.

Angle of Roll = arctan(Rise / Offset)

This angle tells the pipefitter how much to rotate the fitting from a perfectly horizontal or vertical plane to ensure the pipe heads in the correct diagonal direction.