Gear Dimensions Calculator

When to use this CAD/mechanical design tool

• Use before blocking out a gear envelope in CAD.
• Use when checking module or diametral-pitch assumptions.
• Use before moving to spur, helical, shaft, or manufacturing review.

How to use

1. Enter one mechanical-design case using typed dimensions, counts, RPM values, tolerances, or drafting selections.
2. Click the exact action button for the selected tool; default values, typing, URL-prefilled values, and worked examples do not generate results automatically.
3. Review the output cards, warnings, assumptions, visual summary, copy text, and downloads before using the result in CAD, drawing, supplier, or inspection workflow.
4. Verify final values against applicable standards, supplier catalogs, validated CAD documentation, manufacturing limits, inspection practice, and qualified engineering review.

Input guide

Unit system and gear basis

Metric mode uses module; inch mode or diametral-pitch mode uses teeth divided by DP.

Number of teeth

Positive integer greater than five for a basic external gear estimate.

Pressure angle and face width

Recorded for review and warnings; detailed tooth strength and mesh compatibility still need design review.

Notation

Output interpretation

• Use pitch diameter for center distance planning.
• Use outside and root diameter as preliminary CAD envelope values.
• Use warnings to identify low tooth count or nonstandard pressure-angle review.

Supported CAD/mechanical design use cases

• External gear planning
• Module and DP checks
• CAD envelope estimates

Unsupported patterns

• Tooth profile generation
• AGMA or ISO strength rating
• backlash/contact-ratio optimization
• gear train optimization

How to interpret the output

• Pitch diameter controls center-distance planning.
• Outside diameter defines the approximate gear envelope.
• Root diameter is an estimate and needs tooth-system verification.

CAD and mechanical-design guidance

• Use one unit convention per calculation.
• Check mating gear module or DP and pressure angle.
• Treat root diameter as preliminary until tooth system and cutter details are confirmed.

Worked examples

Assumptions

• Inputs are typed planning values and are not extracted from CAD files, supplier catalogs, drawings, PLM, CAM, ERP, or inspection systems.
• Metric calculations use millimetres unless the output explicitly states another unit; inch calculations use inches unless the output explicitly states another unit.
• The result is a preliminary calculator or drafting helper and not a certified standards database, CAD kernel, inspection report, or supplier approval.
• Full-depth external gear planning formulas are used.
• Addendum is treated as one module or one over DP; dedendum is treated as 1.25 times addendum.

Practical guidance

• Use the Spur Gear Calculator when a mating gear and center distance are known.
• Use the Helical Gear Calculator when helix angle and normal/transverse geometry matter.

Common mistakes

• Mixing module and diametral pitch.
• Using outside diameter as pitch diameter.
• Ignoring low-tooth-count undercut review.

Limitations

• No tooth flank, cutter, backlash, strength, noise, lubrication, material, heat-treatment, or contact-ratio calculation is performed.
• ScholarTool CAD and mechanical-design calculators provide general engineering calculation and planning support. They do not replace supplier requirements, certified standards, CAD software documentation, manufacturing review, inspection standards, or professional engineering judgement.
• The tool does not open, upload, parse, repair, or validate CAD files, drawings, STEP, STL, DXF, DWG, CAM, or CNC data.
• The tool does not perform strength certification, fatigue validation, finite-element analysis, supplier catalog selection, standards compliance certification, or inspection programming.

Related workflow links