Bolt Circle Calculator – Measure Bolt Hole Circle

A bolt circle calculator is used to compute the precise layout of bolt holes in a circular pattern, particularly in automotive, machinery, and construction industries.

For Example:

Wheel rim design: Calculating bolt patterns for different vehicle models.

Flange connections: Determining bolt placement in piping systems.

Industrial machinery: Ensuring proper alignment of components in large equipment.

Bolt Circle Calculator

Number of Bolts	Chord Length (inches)	Calculated BCD (inches)	Conversion to mm
4	3.5	4.95	125.73
5	4.2	6.66	169.16
6	3.8	7.36	186.94
8	2.9	7.82	198.63

Conversion equation: mm = inches *25.4

Bolt Hole Circle Formula

The formula for calculating bolt circle diameter (BCD) is:

BCD = Chord Length / (2 * sin(180° / Number of Bolts))

Where:

• BCD is the bolt circle diameter
• Chord Length is the distance between two adjacent bolt centers
• Number of Bolts is the total bolts in the circle

Example: For a 5-bolt pattern with a chord length of 3 inches: BCD = 3 / (2 sin(180° / 5)) ≈ *4.75 inches

How do you measure a bolt circle converter?

Measuring a bolt circle involves several steps:

Count the bolts: Determine the total number of bolts in the circle.

Measure chord length: Find the distance between two adjacent bolt centers.

Use a bolt circle converter: Input the measurements into a calculator or use the formula.

Example: For a 6-bolt pattern:

1. Count 6 bolts
2. Measure 4.5 inches between adjacent bolts
3. Use the formula: BCD = 4.5 / (2 sin(180° / 6)) ≈ *5.2 inches

What is bolt circle diameter?

Bolt Circle Diameter (BCD) is the diameter of an imaginary circle passing through the center of all bolt holes in a circular bolt pattern.

In a car wheel with a 5×114.3mm bolt pattern:

5 represents the number of bolts

114.3mm is the bolt circle diameter

This measurement is crucial for ensuring proper fitment of wheels to vehicles or components in machinery.

How do you measure the bolt circle on a 4 bolt wheel?

For a 4-bolt wheel:

Measure diagonally: Find the distance between two opposite bolt holes.

Apply the formula: BCD = Diagonal Measurement / √2

If the diagonal measurement is 100mm: BCD = 100 / √2 ≈ 70.71mm

What is the math for bolt pattern?

The bolt pattern math involves trigonometry and geometry:

1. Angle between bolts: 360° / Number of Bolts
2. Chord length formula: Chord = 2 BCD sin(Angle / 2)
3. BCD formula: BCD = Chord / (2 * sin(180° / Number of Bolts))

For a 6-bolt pattern with a 5-inch BCD:

Angle = 360° / 6 = 60°

Chord = 2 5 sin(60° / 2) ≈ 2.5 inches

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