The Pitch Circle Diameter (PCD) is the diameter of the circle which passes through the centre of all the studs, wheel bolts or wheel rim holes. The easiest way calculate the PCD is as follows: 1) Identify the size of rim or tyre size. (This helps to narrow down the likely PCD sizes) 2) Measure the distance 'S' between two adjacent studs from the centre of each hole. 3) Using the calculator enter the number of studs/holes and  'S' and press 'calculate'. 3) Using the relevant diagram depending on the number of studs you have you should be          able to identify the correct PCD. Note: Imperial sizes are commonly used on UK trailers whereas European trailers use metric.
4 Stud	5 Stud	6 Stud

PCD Calculator
Select Number of Studs/Holes		Please Select 3 4 5 6
Enter measurement S in millimetres
Pitch Circle Diameter (PCD) =		mm

Rim Size Studs     S   PCD   8" Rim 3 76.90mm   88.8mm     3 95.26mm   110mm     4 70.71mm   100mm   4 71.84mm   101.6mm (4")   4 81.32mm   115mm   4 91.92mm   130mm         10" Rim 4 70.71mm   100mm     4 71.84mm   101.6mm (4")     4 79.20mm   112mm     5 65.83mm   112mm     4 81.32mm   115mm     4 91.92mm   130mm     4 98.78mm   139.7mm (5½")           12" Rim 4 70.71mm   100mm     4 71.84mm   101.6mm (4")     5 65.83mm   112mm     4 91.92mm   130mm     4 98.78mm   139.7mm (5½")     5 82.29mm   140mm     5 97.04mm   165.1mm (6½")           13" Rim 4 70.71mm   100mm     4 79.20mm   112mm     5 65.83mm   112mm     4 91.92mm   130mm     4 98.78mm   139.7mm (5½")     5 82.29mm   140mm     5 97.04mm   165.1mm (6½")           14" Rim 4 70.71mm   100mm     5 65.83mm   112mm     5 82.29mm   140mm     5 89.58mm   152.4mm (6")     6 102.5mm   205mm           16" Rim 5 97.04mm   165.1mm (6½")   PCD Calculation Formula 4 Stud PCD = S   0.7071             5 Stud PCD = S   0.5878               6 Stud PCD = S   0.5