How to Calculate the Compression Spring Expanded Coil Diameter

One circle in the spring is one coil.

A compression spring is a spring that can expand or contract based on the pressure put on the spring. The spring has several coils to allow the spring to change sizes. A compression spring has two diameters, an outside and an inside diameter. The difference is the width of a coil. The inside diameter measures from the inside of the coil to the opposite inside part of the coil. The outside diameter measures from the outside of a coil to the opposite outside of the coil.

Instructions

Inside Diameter

1. Measure or find the width of a coil. The width will normally be labeled when you buy the cable. For example, assume a coil has a width of 1 inch. For the width, assume you spread the cable out so it is flat. The width is then from side of the wire to the other and does not vary based on the length of the cable.

2. Multiply the width of the coil by two. In the example, 1 inch x 2 = 2 inches.

3. Measure the outside diameter. In the example, assume the outside diameter equals 6 inches.

4. Subtract the result from Step 2 from the measurement in Step 3. In the example, 6 inches - 2 inches = 4 inches. This is the inside diameter.

Outside Diameter

1. Measure or find the width of a coil. The width will normally be labeled when you buy the cable. For the width, assume you spread the cable out so it is flat. The width is then from side of the wire to the other and does not vary based on the length of the cable.

2. Multiply the width of the coil by two. In the example, 1 inch x 2 = 2 inches.

3. Measure the inside diameter. In the example, assume the inside diameter equals 6 inches.

4. Add the result from Step 2 to the measurement in Step 3. In the example, 6 inches + 2 inches = 8 inches. This is the outside diameter.

Tips & Warnings

• It is easier to measure the inside and outside diameter with a ruler or tape measure.

References

• Leeco Spring: About Leeco