Bolt Circle Calculator (BCD / PCD)

Bolt circle diameter — also called pitch circle diameter (PCD) — is the diameter of the imaginary circle that passes through the centers of all the wheel bolts or studs. A "5x114.3" wheel means 5 lugs on a 114.3 mm bolt circle. This calculator finds BCD from a center-to-center measurement between two adjacent bolts, or reverses it: BCD from the known diameter to the exact spacing and X/Y coordinates of every hole.

For n evenly spaced lugs and adjacent center-to-center spacing c, the formula is BCD = c / sin(pi/n), where the angle is in radians. Each lug sits on a circle of radius BCD/2, and the chord between neighbors is 2R x sin(pi/n) — solving for BCD gives the formula. Example: 5 lugs with 115.0 mm measured between adjacent bolt centers gives BCD = 115.0 / sin(36 degrees) = 195.65 mm.

On a 5-lug wheel there is no bolt directly opposite, so measure center-to-center between two ADJACENT bolts with a caliper, then multiply by 1.7013 (that is 1/sin(36 degrees)). Example: if you measure 67.18 mm between neighbors, BCD = 67.18 x 1.7013 = 114.29 mm — almost certainly a 5x114.3 pattern. Measure to the centers, not the edges, and repeat across two or three gaps to average out error.

Even-numbered patterns are easy: pick two bolts directly across from each other and measure center-to-center — that distance IS the bolt circle diameter. A 6-lug hub measuring 139.7 mm across opposite studs is 6x139.7, and a 4-lug wheel measuring 100 mm across is 4x100. No formula needed; the calculator's reverse mode still helps you get the adjacent spacing and the hole coordinates for machining.

Reverse the formula: spacing = BCD x sin(pi/n). For 5x114.3: 114.3 x sin(36 degrees) = 67.18 mm between adjacent bolt centers. For 4x100 the same reversal gives 100.0 x sin(45 degrees) = 70.71 mm, and for 6x139.7 it is 139.7 x sin(30 degrees) = 69.85 mm — exactly half the diameter, which is why 6-lug spacing is so easy to check.

Enter your lug count and BCD in the Layout tab and the calculator lists every hole's coordinates from the wheel center, with hole 1 at the top (12 o'clock) and the rest numbered clockwise. For 5x114.3 (radius 57.15 mm): hole 1 is at (0.00, 57.15), hole 2 at (54.35, 17.66), and so on — ready to copy into a CNC program or a drill template. The angular step between holes is 360/n, so 72 degrees for 5-lug.

Nothing — BCD (bolt circle diameter) and PCD (pitch circle diameter) are two names for the same measurement. "Pitch circle" comes from gear and flange engineering, where the pitch circle is the reference diameter for a ring of fasteners; "bolt circle" is the wheel industry's term. A 5x114.3 wheel and a 5-lug 114.3 mm PCD hub are the same thing, and this calculator accepts either term.

The patterns you will meet most often: 4x100 (small cars), 5x100, 5x108, 5x112 (European), 5x114.3 (Japanese/Korean, also written 5x4.5"), 5x120 (BMW), 6x139.7 (many pickups and SUVs, also 6x5.5"), 8x170 and 8x180 (heavy-duty trucks), 8x165.1 (8x6.5" classic truck). The calculator's pattern finder matches your measurement against a built-in database and flags the closest standard pattern within 1.5 mm.

Aim for 0.1-0.2 mm with a digital caliper: a 0.5 mm error in adjacent spacing on a 5-lug wheel becomes about 0.85 mm of BCD error (multiplied by 1.7013). That is enough to confuse 5x114.3 with 5x115 — they differ by only 0.7 mm. Measure center-to-center carefully, average two or three gaps, and let the pattern finder confirm which standard pattern you land on.

Divide-and-convert: 5 lugs on a 4.5-inch circle. 4.5 in x 25.4 = 114.3 mm, so 5x4.5" is exactly 5x114.3. Other imperial classics: 5x4.75" = 120.65 mm, 6x5.5" = 139.7 mm, 8x6.5" = 165.1 mm, 5x5" = 127 mm. Switch the calculator to imperial mode and it does all conversions with the exact 25.4 mm/inch factor, both for inputs and for the coordinate table.

Use imperial mode: enter the spacing in inches and the result comes out in inches too. Example: 2.640 in between adjacent studs on a 5-lug wheel gives BCD = 2.640 / sin(36 degrees) = 4.491 in (about 114.1 mm). Or convert the easy way: 4.500 in x sin(36 degrees) = 2.645 in adjacent spacing for a 5x4.5" (5x114.3) wheel.

With an odd number of lugs, no two bolts sit 180 degrees apart. The widest gap you can measure on a 5-lug wheel is between bolts two steps apart: BCD x sin(72 degrees). On a 5x114.3 that is 114.3 x 0.9511 = 108.71 mm — only about 5% less than the diameter, which is why eyeballing it as "the diameter" is a classic mistake. Stick to adjacent spacing for 5-lug, or use the formula in reverse.

Yes — the math is identical for any ring of equally spaced holes: trailer hubs (common 5x114.3, 6x139.7, 8x165.1), machinery flanges, and pipe flanges with 8 or more bolt holes. Enter any lug count from 3 to 8 and the same chord formula applies. For 8-lug the multiplier is 2.6131, so adjacent spacing on an 8x170 flange is 170 / 2.6131 = 65.06 mm.

It is just 1/sin(36 degrees) written as a shortcut: BCD = adjacent spacing x 1.7013 for any 5-lug pattern. The full set of multipliers is 3-lug: 1.1547, 4-lug: 1.4142, 5-lug: 1.7013, 6-lug: 2.0000, 8-lug: 2.6131. The calculator applies the exact sine rather than the rounded multiplier, so its results are good to 0.01 mm — better than the shortcut when you are machining.

No. Bolt pattern (e.g. 5x114.3) describes where the lug holes sit; hub bore is the diameter of the center hole that centers the wheel on the hub. Two wheels can share a 5x114.3 pattern but have different hub bores (e.g. 73.1 mm vs 67.1 mm) — the smaller-bore wheel will not fit the larger hub. Always check pattern, hub bore, offset, and load rating together; a correct bolt circle alone does not guarantee fitment.

No — even 1 mm off means the studs will not pass through the holes without forcing, and forcing a wheel onto mismatched studs is dangerous. Adapters exist but change offset and add failure points. This is why the calculator flags the nearest standard pattern: if your measurement lands between 5x114.3 and 5x115, re-measure carefully instead of guessing, because those two do not interchange.