Gear module calculator
Determine spur gear module from pitch or outside diameter and tooth count. Useful when measuring unknown gears before modelling or configuring a replacement.
- Inputs
- Pitch diameter, Number of teeth
- Result
- m = d / z
Engineering toolbox
Engineering calculators for gears, threads and dimensions
This engineering toolbox supports practical checks and conversions for gears, threads and dimensional units. It is built for workshops, designers, repair projects and 3D printing workflows: calculate module, pitch diameter, center distance, TPI, tap drill diameter and inch-to-millimetre values directly in the browser without installing software. Each calculator keeps units, formulas, examples and assumptions visible, so the result is easy to verify. The values can be used as preparation for configurable products and replacement parts; when a configurator cannot be prefilled safely, the calculated parameters remain clear and copyable.
Gears6 tools
Determine spur gear module from pitch or outside diameter and tooth count. Useful when measuring unknown gears before modelling or configuring a replacement.
Threads6 toolsConvert TPI to metric thread pitch or pitch to TPI, including thread counts over 10 mm and one inch.
Units and conversions2 toolsConvert millimetres to decimal inches and selectable fractional inches, including rounding error and a practical reference table.
Gears
Pitch diameter calculator
Calculate pitch diameter from module and tooth count, with outside diameter, circular pitch and an optional 20° pressure-angle base circle.
- Inputs
- Module, Number of teeth
- Result
- d = m × z
Gear teeth calculator
Find the theoretical tooth count from module and pitch diameter, then compare the nearest whole-tooth alternatives and their dimensional error.
- Inputs
- Pitch diameter, Module
- Result
- z = d / m
Gear outside diameter calculator
Calculate outside diameter for a standard spur gear with no profile shift, plus pitch diameter, addendum and circular pitch.
- Inputs
- Module, Number of teeth
- Result
- da = m × (z + 2)
Gear center distance calculator
Calculate center distance, both pitch diameters and ratio for two external spur gears of the same module, optionally with input speed.
- Inputs
- Module, Driver teeth, Driven teeth
- Result
- a = m × (z1 + z2) / 2
Gear ratio calculator
Calculate gear ratio, output speed, theoretical loss-free output torque and rotation direction for a simple gear pair.
- Inputs
- Driver teeth, Driven teeth
- Result
- i = z2 / z1
Threads
Thread pitch and TPI calculator
Convert TPI to metric thread pitch or pitch to TPI, including thread counts over 10 mm and one inch.
- Inputs
- TPI
- Result
- pitch_mm = 25.4 / TPI; TPI = 25.4 / pitch_mm
Millimetre to inch thread calculator
Convert metric thread diameter and pitch to decimal inch, fractional inch and TPI; similar Unified sizes are only geometric references.
- Inputs
- Nominal diameter, Thread pitch
- Result
- inch = mm / 25.4
Inch to millimetre thread calculator
Convert inch nominal diameter and TPI to millimetres and metric pitch, then compare nearby metric sizes without claiming compatibility.
- Inputs
- Inches, TPI
- Result
- mm = inch × 25.4
Metric tap drill diameter calculator
Estimate metric tap drill diameter from a standard selection or custom diameter and pitch; table values appear only when maintained.
- Inputs
- Nominal diameter, Thread pitch
- Result
- tap drill ≈ nominal diameter − pitch
Metric to UNC/UNF thread comparison
Compare metric threads with nearby UNC and UNF sizes by diameter and pitch. The table shows deviations, not interchangeability.
- Inputs
- Nominal diameter, Thread pitch
- Result
- geometric comparison by diameter and pitch
Internal and external thread dimensions calculator
Calculate simplified basic dimensions for internal and external threads. Results are approximations and do not replace tolerance tables.
- Inputs
- Nominal diameter, Thread pitch
- Result
- minor diameter approximation ≈ nominal diameter − pitch
Units and conversions
Millimetre to inch calculator
Convert millimetres to decimal inches and selectable fractional inches, including rounding error and a practical reference table.
- Inputs
- Millimetres
- Result
- inch = mm / 25.4
Inch to millimetre calculator
Convert decimal, fractional or mixed inch values safely to millimetres and centimetres with a clear calculation line.
- Inputs
- Inches
- Result
- mm = inch × 25.4
What can the calculators be used for?
- unbekannte Zahnräder vermessen
- Ersatzteile vorbereiten
- Achsabstände kontrollieren
- Gewindesteigungen und TPI vergleichen
- metrische und zöllige Maße vergleichen
- Parameter für ein eigenes 3D-Modell vorbereiten
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Configure productEngineering toolbox FAQ
Do two gears need the same module?
Yes, meshing spur gears normally require the same module.
Can I manufacture directly from this result?
Use the value as a calculation and configuration aid. Loaded or standards-critical parts need engineering review.
Are metric and UNC/UNF threads interchangeable?
No. Similar diameters do not mean profile, pitch and tolerance are compatible.
Can I manufacture directly from this result?
Use the value as a calculation and configuration aid. Loaded or standards-critical parts need engineering review.
Engineering calculators for gears, threads and dimensions?
Professional online calculators for gear geometry, thread dimensions, TPI, tap drills, millimetres and inches with formulas, assumptions and product CTAs.