How to calculate the PCD – Pitch circle diameter
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 to calculate the PCD is as follows:
- Identify the size of the rim or tyre size. (This helps to narrow down the likely PCD sizes)
- Measure the distance ‘S’ between two adjacent studs from the centre of each hole. (see diagrams below)
- 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 Studs/Holes | 5 Studs/Holes | 6 Studs/Holes |
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Once you have the measurement of 'S' above, you can easily work out the PCD by using one of the 3 calculations below:
Wheel PCD Measurement Calculation Formula
- 4 Stud PCD = Stud distance divided by 0.7071 to get PCD
- 5 Stud PCD = Stud distance divided by 0.5878 to get PCD
- 6 Stud PCD = Stud distance divided by 0.5 to get PCD
Example:
67.185mm / 0.5878 for a five stud with 1/2″ studs is 114.30mm, which is a Ford Stud Pattern. (highlighted below)
Below is a table of all the common PCD measurements: (All you need to do is measure the adjacent holes as per the diagrams above and match it with the right hand column in the table below)
| Wheel Type | Stud Diameter | Number of Studs | Inches PCD | MM PCD | Centre to Centre of Adjacent Studs | Centre to Centre of Adjacent Studs ('S' above) |
| Commodore | 7/16" | 5 | 120.00 | 2.776" | 70.53 | |
| Ford | 1/2" | 5 | 4 1/2" | 114.30 | 2 5/8" | 67.18 |
| Holden HT HG HK | 7/16" | 5 | 4 1/4" | 107.95 | 2 1/2" | 63.45 |
| Holden HQ HJ HX | 7/16" | 5 | 4 3/4" | 120.65 | 2 13/16" | 70.91 |
| Capri | 7/16" | 4 | 4 1/4" | 107.95 | 3" | 76.33 |
| Cortina/Telstar | 7/16" | 4 | 4 1/4" | 107.95 | 3" | 76.33 |
| Datsun 1600 | 7/16" | 4 | 4 1/2" | 114.30 | 3 3/16" | 80.82 |
| Early Ford | 1/2" | 4 | 4 1/2" | 114.30 | 3 3/16" | 80.82 |
| Ford F100 | 1/2" | 5 | 5 1/2" | 139.70 | 3 1/4" | 82.11 |
| Ford-Jeep | 1.2" | 5 | 5 1/2" | 139.70 | 3 1/4" | 82.11 |
| Gemini | 7/16" | 4 | 100.00 | 2 13/16" | 70.7 | |
| Land Rover | 5/8" | 5 | 6 1/2" | 165.10 | 3 13/16" | 96.98 |
| Land Cruiser 100 Series | 9/16" | 5 | 150.00 | 88.17 | ||
| Land Cruiser 4WD | 1/2" | 6 | 5 1/2" | 139.70 | 2 3/4" | 69.85 |
| Nissan Patrol | 1/2" | 6 | 5 1/2" | 139.70 | 2 3/4" | 69.85 |
| Nissan Navara D40 | 1/2" | 6 | 114.30 | |||
| Mini | 7/16" | 4 | 4" | 101.60 | 2 13/16" | 71.84 |
| Toyota Corona | 7/16" | 4 | 4 1/2" | 114.30 | 3 3/16" | 80.82 |
| Valiant to 71 | 7/16" | 5 | 4" | 101.60 | 2 3/9" | 59.72 |
| Valiant 71 - 72 | 7/16" | 5 | 4 1/2" | 114.30 | 2 5/8" | 67.18 |
Table above: Shows measurements to define the Rim, you only need match either the PCD or the Adjacent dimension, whichever is easier to measure. The common hubs and rims are shown in the table with the FORD highlighted. Some measurements are shown as imperial as they are exact, but the metric sizes are included.