Choosing the right sprocket is crucial for ensuring smooth power transmission, reducing wear, and improving mechanical performance. Whether you’re using industrial equipment, agricultural machinery, motorcycles, or conveyor belts, the correct sprocket size ensures a perfect match with the chain and safe operation.
As a leading global supplier of bearings and power transmission equipment, we frequently receive the same question from our customers: “How are sprockets measured?” In this article, we’ll explain it clearly and professionally so you can confidently choose the right sprocket.
1. Chain Pitch: The Core Measurement
The first and most important dimension is the pitch—the distance between the centers of two adjacent chain pins.
The sprocket pitch must match the chain pitch; otherwise, it won’t function properly.
Common pitch sizes include:
ANSI chain lengths: 25, 35, 40, 41, 50, 60
Motorcycle chain lengths: 420, 428, 520, 525, 530
Matching the tooth pitch ensures correct tooth spacing and smooth engagement with the sprocket.

2. Number of Teeth
The number of teeth on a sprocket affects its performance and function.
More teeth → Higher speed, lower torque
Fewer teeth → Greater torque, faster acceleration
This measurement is simple—just count the number of teeth on the circumference.
3. Bore Diameter (Inner Diameter)
The bore is the center hole that mates with the shaft or hub.
Depending on the machine, the type of bore varies:
Flat bore
Keyed bore
Splined bore
Tapered or tapered bushing bore
Choosing the appropriate bore diameter ensures a secure sprocket installation and prevents vibration during operation.
4. Outer Diameter (OD)
This is the total diameter measured from one tooth tip to the opposite tooth tip.
Outer diameter is especially important in:
Installing sprockets within guards or housings
Checking clearances
Designing compact machine layouts
5. Sprocket Thickness
Each chain series requires sprockets of a specific thickness to match the roller width.
For example:
520 sprocket: approx. 6.35 mm
530 sprocket: approx. 9.53 mm
A chain that is too thin or too thick will cause misalignment or premature wear.
6. Hub Diameter and Hub Width
If the sprocket has an extended hub, you will also need:
Hub outer diameter
Hub width or thickness
These dimensions ensure compatibility with your shaft and prevent interference with surrounding components.
7. Bolt Round Diameter (BCD)
For bolt-mounted sprockets, the bolt round diameter is crucial.
It refers to the diameter of the circle passing through the center of all mounting holes.
Also note:
Number of mounting holes
Hole diameter
Center distance (if needed)
The correct BCD value ensures the sprocket is aligned with the mounting flange or wheel.
8. Offset
Offset refers to the distance the sprocket deviates from its mounting surface.
This helps maintain proper chain alignment—especially in custom machinery, agricultural equipment, and motorcycles.
Knowledge Required for Identifying Sprockets
When customers contact our team to request replacement or custom sprockets, we typically ask for the following information:
Chain pitch
Number of teeth
Bore type and size
Sprocket thickness
BCD + number of holes (if applicable)
Offset (optional, but helpful)
Providing this detail helps us quickly and accurately match or customize the right sprocket.
DFL NSAR is committed to providing high-quality sprockets, bearings, and power transmission components to buyers worldwide. With overseas warehouses and extensive experience in cross-border trade, we help customers obtain the right parts faster at more competitive prices.
If you need standard or custom sprockets, please feel free to contact our team.