Introduction
A bolt circle is the invisible circle that passes through the center of each lug hole on a wheel. Knowing your bolt circle measurement, also called a bolt pattern, is key when buying new wheels for your car or truck. If the bolt pattern doesn't match, the wheel simply won't fit. This bolt circle calculator helps you quickly find the diameter of your bolt circle based on the number of lugs and the distance between them. Whether you're shopping for aftermarket rims, swapping wheels between vehicles, or just checking specs, this tool gives you the answer in seconds — no measuring tape or guesswork needed.
How to Use Our Bolt Circle Calculator
This bolt circle calculator helps you find the exact position of each bolt hole on a wheel or flange. Enter your bolt circle details below, and the tool will give you hole coordinates, a visual diagram, and even NC/G-code output. You can also use the reverse mode to find a bolt circle diameter from a measured distance between holes.
Calculator Mode: Choose between "Bolt Hole Positions" to calculate where each hole goes on a known bolt circle, or "Find Bolt Circle Diameter" to work backward from a measured distance between two adjacent holes. This is helpful when you need to identify an unknown bolt pattern on a wheel or hub.
Unit System: Select either inches or millimeters depending on how your bolt circle is measured. Most American wheel bolt patterns use inches, while many import vehicles use millimeters.
Decimals: Pick how many decimal places you want in your results, from 2 to 6. Use more decimals when you need higher precision for machining or CNC work.
Bolt Circle Diameter (BCD): Enter the diameter of the circle that passes through the center of each bolt hole. For example, a common 5-lug wheel pattern might have a BCD of 4.5 inches or 114.3 mm.
Number of Holes: Enter how many bolt holes are evenly spaced around the circle. Typical wheel bolt patterns use 4, 5, 6, or 8 holes.
Hole Diameter: Enter the size of each bolt hole. This value is used in the diagram and NC code output. Set it to 0 if you only need the center-point locations.
Start Angle: Enter the angle of the first bolt hole, measured from the 3 o'clock position (the +X axis) going counter-clockwise. You can type a simple number like 45 or use degrees-minutes-seconds format such as 64d45m34s. The tool will show you how it reads your input.
Center X Offset and Center Y Offset: Enter these values if the center of your bolt circle is not at the origin point (0, 0). For most basic wheel bolt pattern calculations, you can leave both set to 0.
Measured Distance (Reverse Mode): When using the "Find Bolt Circle Diameter" mode, enter the straight-line or arc distance you measured between two adjacent bolt hole centers.
Distance Type (Reverse Mode): Choose "Chord" if you measured the straight-line distance between two neighboring holes, or "Arc" if you measured along the curved path of the bolt circle. Most people measure the chord since it is easier to do with a ruler or caliper.
Angle Converter Utility: Use this section at the bottom to quickly convert angles between decimal degrees, degrees-minutes-seconds (DMS), and radians. Type a value into any field and click the matching convert button to update the others.
What Is a Bolt Circle?
A bolt circle is an imaginary circle that passes through the center of each bolt hole on a wheel, flange, or any circular part. The bolt circle diameter (BCD), also called the bolt pattern or pitch circle diameter (PCD), is the diameter of that circle. If you have ever shopped for new wheels for your car or truck, you have seen bolt patterns written as something like "5x114.3" or "4x100." The first number is how many bolt holes there are, and the second number is the bolt circle diameter in millimeters.
Why the Bolt Circle Matters for Wheels and Tires
Getting the bolt pattern right is one of the most important steps when buying aftermarket wheels. If the bolt circle diameter does not match your vehicle's hub, the wheel simply will not bolt on. Even being off by a couple of millimeters can make mounting impossible or unsafe. Common bolt patterns include 4x100, 5x114.3, 5x120, 6x139.7, and 8x165.1, but there are dozens of others across different makes and models. Beyond the bolt circle, you should also verify that the tire size is compatible with the new wheels and use a wheel offset calculator to confirm proper fitment and clearance.
How a Bolt Circle Is Calculated
Each bolt hole sits on the circle at an equal angle from the next. The angle between adjacent holes is found by dividing 360° by the number of holes. For example, a 5-lug wheel has holes spaced 72° apart. Once you know the bolt circle diameter and the number of holes, you can find the exact X and Y position of every hole using basic trigonometry:
- X = radius × cos(angle)
- Y = radius × sin(angle)
The calculator above does this math for you instantly. It also figures out the chord length, which is the straight-line distance between the centers of two neighboring bolt holes. This chord measurement is handy because you can physically measure it with a caliper or ruler and then work backward to find the bolt circle diameter. If you need to work with chord lengths or distances between points in other contexts, our distance calculator and arc length calculator can also help.
Measuring Your Bolt Pattern at Home
If you do not know your vehicle's bolt pattern, you can measure it yourself. For wheels with an even number of lugs (4, 6, or 8), measure straight across from the center of one bolt hole to the center of the hole directly opposite it. That measurement is your BCD. For wheels with an odd number of lugs (5 or 7), there is no hole directly across from another. In that case, measure the distance between two adjacent bolt hole centers and use the reverse mode of this calculator to find the bolt circle diameter.
What the Two Calculator Modes Do
The Bolt Hole Positions mode takes a known bolt circle diameter, number of holes, and optional start angle, then gives you the exact coordinates of every hole. This is useful for machining, drilling, or verifying a wheel fitment diagram. The Find Bolt Circle Diameter mode works in reverse. You enter the number of holes and the measured distance between two adjacent holes (either the straight chord or the curved arc length), and it calculates the BCD for you. This is the fastest way to identify an unknown bolt pattern on a wheel or hub.
Quick Tips
- Always double-check units. Bolt patterns in the U.S. market are often listed in millimeters, even on domestic vehicles. Switch between inches and millimeters in the calculator to avoid mistakes.
- Hub-centric vs. lug-centric: Matching the bolt circle is necessary, but also check the center bore size and wheel offset before mounting a new wheel.
- Dual-pattern wheels have two sets of bolt holes for two different BCDs, making them fit a wider range of vehicles.
- The angle converter at the bottom of the calculator lets you quickly switch between decimal degrees, degrees-minutes-seconds, and radians if you need to work with different angle formats.
- When upgrading wheels, also consider how changes affect your tire size, gas mileage, and speedometer accuracy.
- For engine-related projects that involve circular bolt patterns on cylinder heads or flanges, our compression ratio calculator and engine displacement calculator may also come in handy.