S. no. 
To Obtain 
Having 
Rule

1 
Circular Pitch 
Diametral Pitch 
Divide 3.1416 by the Diametral Pitch. 
2 
Diametral Pitch 
Circular Pitch 
Divide 3.1416 by the Circular Pitch. 
3 
Lead (of Worm) 
Number of Threads in worm & Circular Pitch 
Multiply the Circular pitch by the
number of threads. 
4 
Circular Pitch or Linear Pitch 
Lead and number of threads in worm 
Divide the lead by the number of threads 
5 
Addendum 
Circular Pitch 
Multiply the Circular pitch by .3183.

6 
Addendum 
Diametral Pitch 
Divide 1 by the Diametral Pitch.

7 
Pitch Diameter of Worm 
Outside Diameter and Addendum 
Subtract twice the Addendum from the Outside Diameter.

8 
Pitch Diameter of Worm 
Select Standard Pitch Diameter when Designing 
Worm Gears are made to suit the mating worm.

9 
Pitch Diameter of Worm Gear 
Circular Pitch and Number of Teeth 
Multiply the number of teeth in the gear by the Circular Pitch and divide the product by 3.1416. 
10 
Pitch Diameter of Worm Gear 
Diametral Pitch and No. of Teeth 
Divide the number of teeth in gear by the Diametral Pitch

11 
Center Distance between Worm and Worm Gear 
Pitch Diameter of Worm and Worm Gear 
Add the Pitch Diameters of the worm and worm gear then divide the sum by 2.

12 
Whole Depth of Teeth 
Circular Pitch 
Multiply the Circular Pitch by .6866.

13 
Whole Depth of Teeth 
Diametral Pitch 
Divide 2.157 by the Diametral Pitch.

14 
Bottom Diameter of Worm 
Whole Depth and Outside Diameter 
Subtract twice the whole depth from the Outside Diameter

15 
Throat Diameter of Worm Gear 
Pitch Diameter of Worm Gear and Addendum 
Add twice the Addendum to the pitch diameter of the Worm Gear.

16 
Lead Angle of Worm 
Pitch Diameter of the Worm and the Lead 
Multiply the Pitch Diameter of the Worm by 3.1416 and divide the product by the Lead,
the Quotient is the cotangent of the Lead Angle of the Worm.

17 
Ratio 
Number of Starts (or threads) in the Worm and the
number of teeth in
the Worm Gear 
Divide the number of teeth in Worm Gear by number of starts (or threads) in worm.
