Sprocket tooth count & pitch circle
Compare pitch circle diameter and average pitch advance for a selected chain pitch. Change an input to explore the relationship.
Input parameters
Set your values below. The table updates automatically.
Comparison results
Pitch diameter is through pin centers, not tooth tips. This table does not define a manufacturing tooth profile.
| Teeth | Pitch diameter (mm) | Pitch diameter (in) | Advance / rev (mm) |
|---|---|---|---|
| 10.00 | 41.10 | 1.62 | 127 |
| 12.00 | 49.07 | 1.93 | 152.4 |
| 15.00 | 61.08 | 2.40 | 190.5 |
| 18.00 | 73.14 | 2.88 | 228.6 |
| 20.00 | 81.18 | 3.20 | 254 |
| 24.00 | 97.30 | 3.83 | 304.8 |
| 30.00 | 121.5 | 4.78 | 381 |
| 40.00 | 161.87 | 6.37 | 508 |
| 60.00 | 242.66 | 9.55 | 762 |
How this table is calculated
pitch diameter = p/sin(π/N); advance per revolution = NpRows use the same assumptions while varying the value in the first column. Input-unit controls change the units used to enter values; column headers always state the output units.
How to read this comparison
Pitch remains fixed while tooth count changes. Pitch diameter passes through pin centers; advance per revolution counts straight chain pitches. Their relationship differs from a circular circumference calculation.
A worked example with the initial inputs
At the initial 0.5-inch pitch, the 12-tooth row gives 0.5/sin(15°) ≈ 1.93185 inches or 49.069 mm pitch diameter. Chain advance is exactly 12 × 12.7 = 152.4 mm per revolution in the nominal geometry.
The live table changes when you edit its controls.
Use the interactive calculator to explore more scenarios, units and relevant inputs.
Frequently asked questions
Can I use pitch-circle diameter as outside diameter?
No. Outside diameter reaches tooth tips and requires the correct tooth-profile specification. This chart supplies pin-center geometry, not manufacturing dimensions.
Why do input controls and column headers show different units?
The unit toggle changes how you enter dimensional inputs. Each output column keeps its stated unit so you can compare values consistently. Read the column header before copying a result.
Understand the method in more detail
Motorcycle chain length and center distanceA two-sprocket chain-length estimate combines straight chain spans with the chain wrapped around each sprocket. The result is a pitch count that must fit the available axle adjustment.
Sprocket pitch diameter from polygon geometryThe pitch circle passes through the chain pin centers seated on a sprocket. Its diameter differs from the outside diameter measured across the tooth tips.Source and assumptions
Two-sprocket chain approximation and even-pitch selection. Sprocket geometry is independently derived from the regular polygon chord.
Renold — Transmission chain installation & designer guideRead the calculation methodology for model scope, unit conventions and review status.