This bolt pattern calculator finds the bolt circle diameter (BCD) — the diameter of the circle through the center of every bolt — from the number of bolts and their spacing. Enter your measurements above to get the exact pattern for a wheel, hub, or flange.
How is bolt circle diameter calculated?
For evenly spaced bolts, the BCD comes from the adjacent bolt-center spacing and the bolt count:
BCD = S ÷ sin(180° ÷ n)
- S — distance between the centers of two adjacent bolts
- n — number of bolts
For 4-bolt patterns you can simply measure straight across between opposite bolt centers.
Example calculation
For a 5-lug pattern with 2.645 in between adjacent bolts:
- BCD = 2.645 ÷ sin(36°) = 2.645 ÷ 0.5878 = 4.5 in (114.3 mm)
That is the common 5×114.3 pattern.
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Frequently Asked Questions
How do I measure a bolt pattern?
Count the bolts and measure the spacing. For even patterns, measure straight across between two opposite bolt centers; for odd patterns like 5-lug, use the adjacent-bolt formula.
How do I calculate 5-lug bolt pattern?
Divide the distance between two adjacent bolt centers by the sine of 36 degrees. A 2.645-inch spacing gives a 4.5-inch (114.3 mm) bolt circle.
What does 5×114.3 mean?
It means 5 bolts on a bolt circle diameter of 114.3 mm (4.5 inches). The first number is the bolt count, the second is the BCD.