Enter the lead and mean diameter of a helix or screw into the calculator. The calculator will display the lead angle of the helix.

Lead Angle Formula

The following formula is used to calculate the lead angle of a helix or screw.

LA = arctan (L/PI*D)
  • Where LA is the lead angle
  • L is the lead
  • D is the mean diameter of the helix

To calculate a lead angle, take the lead divided by pi, then multiply by the diameter. Finally, take the arc tangent of this result.

Lead Angle Definition

A lead angle is defined as the angle between a thread and the plane of rotation the thread sits on. This can also be applied to helixes.

How to calculate lead angle?

How to calculate a lead angle

  1. First, measure the lead of the helix

    The lead of the helix is the axial distance traveled during one complete turn along a helix or screw thread. Measure this is whichever is your preferred unit, just make sure the units are consistent.

  2. Next, measure the mean diameter

    This is the average diameter of the helix, usually taken through measure the total diameter and dividing by two.

  3. Finally, calculate the lead angle

    Enter the information from steps 1 and 2 into the equation above to calculate the lead angle.


What is a lead angle?

A lead angle is defined as the angle between the helix or thread and the plane of rotation. The plane of rotation is most often considered the axial plane.

What is a thread?

A thread is a type of physical structure used to hold screws in place when assembled. It’s a helical type structure that revolves around a cylinder and moves down along the axial length.