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ChainSprocketCalc

Sprocket Calculator: Ratio, Size & Chain Load

One dashboard for a chain drive: drive ratio, output speed, chain length, sprocket diameters, chain speed and a tension check from your power.

Presets

Sprocket & Drive Inputs

Ratio 2.647:1
PD 3.401 · OD 3.718 in
T
PD 8.96 · OD 9.313 in
T
30–50P: 18.8–31.3
in
Driver rpm
Tire Ø (0 = none)
in
Transmitted power

Drive Ratio

2.647:1

Output:661.1 rpm

Chain Length

96L

Wrap:164° (7.7T)

Working Chain Pull

160lbf28.1× tensile

Metric:711 N

Chain tension is 28.1× below the minimum tensile strength, within the 6:1 guideline.

Working load is usually kept to about a sixth of the average tensile strength; ANSI and ISO figures here are minimums, so this check is conservative. Tight-side tension is 772 N (711 N working + 62 N centrifugal). This is a screening check, not a rating: check your chain maker's power tables, which include service factors.

Chain speed and polygon effect

Chain speed

1549 ft/min

7.87 m/s

Polygon effect

1.73%

Smooth

Lubrication (indicative)

Type C: Forced-Feed Oil Stream Lubrication (High Speed)

Chain makers choose lubrication from chain size and sprocket rpm, so use their chart for the final choice.

Sprockets at the same scale

Driver and driven sprocket dimensions for #50 chain
Dimension (in)Driver 17TDriven 45T
Pitch diameter3.4018.96
Outside diameter (approx.)3.7189.313
Root diameter3.0018.56
Caliper diameter (odd / odd)2.9878.554
Max hub diameter2.6888.283
Shaft torque (Nm)30.577.6

How a Chain Drive Is Calculated

Ratio and speed come from the tooth counts, size from the pitch, and load from the power and chain speed. Each part has its own calculator if you need to go deeper, such as the chain length calculator for link count or the compound sprocket ratio calculator for jackshaft drives.

Ratio, speed and tension

Ratio = N₂ / N₁
Output rpm = Input rpm × N₁ / N₂
Chain speed v = N₁ × P × rpm
Working pull F = Power / v
N1
= driver teeth, N₂ the driven teeth
P
= chain pitch

Sizing the chain for the load

Compare the total tight-side tension with the chain's average tensile strength. A ratio of at least 6:1 is the usual guideline. Below it, use a larger or multi-strand chain. Chain makers' power tables also apply service factors for shock loads and long running hours, which this check does not.

Polygon Effect by Tooth Count

Chain speed varies as each tooth engages, and the variation falls quickly with more teeth. Small sprockets suit slow drives only. Check wrap and diameters of your choice with the sprocket diameter calculator.

Speed variation from the polygon effect by driver tooth count
Driver teethSpeed variationCharacter
9T6.42%Noticeable at speed
11T4.22%Noticeable at speed
13T2.99%Noticeable at speed
15T2.23%Noticeable at speed
17T1.73%Smooth
19T1.38%Smooth
25T0.79%Smooth
32T0.48%Smooth
45T0.24%Smooth

Sprocket Calculator FAQ

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