Power transmission calculator

Roller Chain Sprocket Dimensions

Calculate pitch, outside, root, and bore dimensions for an ANSI roller-chain sprocket, with plate-fit guidance and a live profile.

Build a laser-cut plate sprocket

Select a roller chain, then set its tooth fit, bore, and plate thickness.

Set all
rpm

Generated dimensions

Pitch diameter
2.8794 in
Outside diameter
3.1356 in
Generated root diameter
2.5628 in
Roller seat radius
0.1583 in
Chain speed
225 ft/min
Plate material
Steel 1008
Plate thickness
0.187 inRecommended fit
Chain side clearance
0.0628 in per side

ANSI roller chain dimensions

Recommended plate thickness leaves side clearance inside the chain.

ANSI #40 selected
ChainPitchRoller diameterInside widthIdeal plate
ANSI #250.250 in · 6.35 mm 0.130 in · 3.302 mm 0.125 in · 3.175 mm 0.098 in · 2.5 mm
ANSI #350.375 in · 9.525 mm 0.200 in · 5.08 mm 0.188 in · 4.763 mm 0.118 in · 3 mm
ANSI #400.500 in · 12.7 mm 0.312 in · 7.925 mm 0.313 in · 7.938 mm 0.250 in · 6.35 mm
ANSI #410.500 in · 12.7 mm 0.306 in · 7.772 mm 0.250 in · 6.35 mm 0.188 in · 4.763 mm
ANSI #500.625 in · 15.875 mm 0.400 in · 10.16 mm 0.375 in · 9.525 mm 0.313 in · 7.938 mm
ANSI #600.750 in · 19.05 mm 0.469 in · 11.913 mm 0.500 in · 12.7 mm 0.375 in · 9.525 mm

Laser-cut profile preview

The B29.1 profile uses a roller seating curve, working curve, tangent flat, and topping curve. The dashed roller shows engagement at the pitch circle.

ASME B29.1 profile

Generate the manufacturing file

100% in-browser

OpenCascade builds and reopens the STEP entirely in your browser. No dimensions, settings, or geometry are uploaded.

Laser cut it at Fabworks

We will generate the STEP if needed, add it to a new quote, and open that quote in a new tab for material, finish, and quantity.

The STEP uses the ASME B29.1 theoretical tooth form and catalog outside-diameter truncation. Manufacturing tolerances, material, heat treatment, alignment, lubrication, and application loads still require engineering review.

Quick answer

How this sprocket dimensions calculator works

Roller-chain sprocket dimensions are controlled by chain pitch, roller diameter, tooth count, bore, and the selected tooth-form clearance. The live profile and dimension table update together from the same generated geometry.

How to use the calculator

  1. 1Choose the ANSI roller-chain size or enter custom pitch, roller diameter, and inside width.
  2. 2Enter the tooth count, bore, shaft speed, and nominal or laser-clearance tooth fit.
  3. 3Choose a Fabworks plate material and thickness that fits inside the chain’s inner width.
  4. 4Review pitch, outside, root, and bore dimensions together with chain speed and the generated profile.

Worked example

#40 chain, 18-tooth sprocket

Inputs
ANSI #40 chain with 0.500 in pitch, 0.312 in rollers, and 18 teeth.
Result
Pitch diameter ≈ 2.879 in and planning outside diameter ≈ 3.136 in.

The calculator uses the selected chain geometry and tooth count for the profile; bore, clearance, relief, and plate thickness remain editable.

Common questions

What to know before using the result

How is sprocket pitch diameter calculated?
Pitch diameter equals chain pitch divided by the sine of 180 degrees divided by tooth count. Increasing tooth count increases pitch diameter for the same chain.
Which plate thickness should I use?
Plate must fit between the chain’s inner side plates with appropriate side clearance. The selector marks the closest available Fabworks stock thickness that stays within the selected chain width.
Is this profile for roller chain or a timing belt?
It is for roller chain. HTD and other synchronous-belt pulley profiles use different tooth geometry and should not use these dimensions.

Formula

Dₚ = p ÷ sin(180° ÷ N)

Pitch diameter Dₚ is set by chain pitch p and tooth count N. The generated profile follows the ASME B29.1-2011 (R2022) theoretical tooth construction: roller seating curve, working curve, tangent flat, topping curve, and catalog outside-diameter truncation.

Engineering references

Assumptions and limits

  • Presets use nominal ANSI roller-chain pitch and roller diameter values covered by ASME B29.1.
  • The browser-generated STEP is a closed, uniform-thickness plate sprocket with a round bore.
  • Nominal fit uses the standard theoretical minimum seating curve; optional clearance and tip relief are deliberate deviations for prototype tuning.
  • Hubs, keyways, bore tolerances, material, heat treatment, and high-speed applications require an engineering review.
  • Chain speed assumes the sprocket rotates at the entered shaft speed without slip.
Educational estimate
Use this result for learning and early design exploration. Verify safety-critical or production decisions with the governing standard, material data, real tooling, and a qualified engineer.

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