Taper Calculator

Find the taper (slope) of a conical part.

How the Math Works

The Taper Calculator uses the formula TPF = (large - small) ÷ length × 12 to determine the taper per foot. This equation subtracts the smaller diameter from the larger diameter to find the total difference in size, then divides by the length over which the taper occurs. Multiplying by 12 converts the measurement from inches to feet, since there are 12 inches in a foot. The result, TPF, represents how much the diameter changes per foot of length along the tapered section.

Practical Applications

To use this calculator practically, measure the larger diameter, smaller diameter, and the length of the tapered section in inches. For example, if a conical shaft has a large diameter of 2.5 inches, a small diameter of 1.5 inches, and a tapered length of 8 inches, the calculation would be (2.5 - 1.5) ÷ 8 × 12 = 1.5 TPF. This information helps determine if your workpiece meets specifications or what drill bit size you need for a counterbore operation.

Day-to-Day Use

This calculation is valuable in workshops and manufacturing settings where precision matters. Whether you're turning a wooden dowel for a tight-fitting joint, creating a metal cone for plumbing work, or repairing a tool with a tapered shank, knowing the taper per foot ensures parts fit together properly. It prevents costly mistakes from ordering wrong-sized components and helps achieve professional-quality results in DIY projects, furniture making, and mechanical repairs.

Worked example

2→1.5 in over 6 in → 1.0 in/ft (≈4.8°).

FAQ