These calculators can be used to calculate the Outside Diameter and Centre Distance of spur gears and pinions.

Please note that these calculators should ONLY be used for spur gears and NOT for helical gears.

The calculators can be used for spur gears with the following tooth sizes:

• 48 DP
• 60 DP
• 64 DP
• 72 DP
• 96 DP
• 100 DP
• 0.2 MOD.
• 0.3 MOD.
• 0.4 MOD.
• 0.5 MOD.
• 0.6 MOD.

Note for calculating sizes when using 'Corrected gears'

'Corrected gears' are indicated by a * mark which follows their actual number of teeth, following this in brackets will be the number of teeth which should be used when doing any calculations involving these gears. (see example below)

Example to calculate the centre distance of two 64 dp spur gears.

To calculate the centre distance for a 13T * (14T) spur gear and a 22T spur gear.

The number of teeth which should be entered are 14T and 22T, this will give the correct centre distance. If you enter 13T and 22T the centre distance will be incorrect.

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Outside Diameter Calculator

How to use Spur Gear Outside Diameter Calculator:

1. Select tooth size from dropdown list.
2. Enter the number of teeth for the spur gear.
3. Click on the 'Calculate outside diameter' button.
4. The result will be displayed on the dimension line in both metric and imperial sizes.
5. To do another calculation click on the 'Clear calculator' button and start again at step 1.

The outside diameter that the calculator returns is for the gear at its correct size. However, this size will vary slightly due to manufacturing tolerances.

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Centre Distance Calculator

How to use Spur Gear Centre Distance Calculator:

1. Select tooth size from dropdown list.
2. Enter the number of teeth for each of the two spur gears.
3. Click on the 'Calculate centre distance' button.
4. The result will be displayed on the dimension line in both metric and imperial sizes.
5. To do another calculation, click on the 'Clear calculator' button and start again at step 1.

The centre distance that the calculator returns is for the two gears in tight mesh. Some allowance will have to be made for backlash. This amount will vary depending on the tooth size of the gears and the manufacturing tolerances. However, adding 0.004"[0.1 mm] to the calculated centre distance, should be enough.