Thread Pitch Ratio Calculator

Calculate the thread pitch ratio between two screws or threaded components. Supports multiple units for thread length (µm, mm, cm, m, in, ft, yd) and pitch (µm, mm, cm, in). Enter thread length and number of threads or TPI to compute pitch. Results are shown as screw thread visualizations in chart view by default.

Thread Pair 1

Result

Detailed Steps

Thread Pitch Ratio Visualization

Formula

Thread Pitch and Ratio Calculations

Thread pitch calculation:

P = L ÷ n

Where:

  • P = Thread pitch (µm, mm, cm, in)
  • L = Thread length (µm, mm, cm, m, in, ft, yd)
  • n = Number of threads

Thread pitch from TPI (imperial):

P = 1 ÷ TPI

Thread pitch ratio:

Ratio = Driven Thread Pitch ÷ Driver Thread Pitch (Metric, in mm)
Ratio = Driver TPI ÷ Driven TPI (Imperial)

Notes:

  • Metric: Pitch is converted to mm for ratio calculations.
  • Imperial: TPI is used directly, or pitch is converted to inches.
  • Typical values:
    • Metric threads: 0.5–6 mm (coarse/fine threads)
    • Imperial threads: 4–80 TPI
  • A ratio > 1 (metric) or < 1 (imperial) means slower motion (higher force); < 1 (metric) or > 1 (imperial) means faster motion (lower force).

How to Use the Thread Pitch Ratio Calculator

  1. Select the unit system (Metric or Imperial).
  2. For each thread pair, enter the driver and driven thread pitches with their units (µm, mm, cm, in), or compute them using thread length (L, in µm, mm, cm, m, in, ft, yd) and number of threads (n) with P = L ÷ n, or TPI with P = 1 ÷ TPI (imperial).
  3. Add more thread pairs as needed using the “Add Thread Pair” button.
  4. Select display mode (Chart View is default).
  5. Click “Calculate” to view results, including thread pitch ratios and screw thread visualizations. Learn more about threads.

Frequently Asked Questions (FAQs)

What is thread pitch?

Thread pitch is the distance between the same point on two adjacent threads, such as between two crests or roots, measured in µm, mm, cm, or inches.

How is thread pitch ratio calculated?

In metric units, ratio = driven pitch ÷ driver pitch (both in mm). In imperial units, ratio = driver TPI ÷ driven TPI, indicating relative motion or force.

How do I measure thread pitch?

Measure the distance between two crests using a ruler or caliper. For imperial units, count threads over 1 inch to get TPI, then calculate pitch as P = 1 ÷ TPI.

How do I calculate pitch from thread length and number of threads?

Use P = L ÷ n, where L is the thread length (in selected unit) and n is the number of threads. The calculator converts units automatically.

Why use the chart view?

It visualizes thread pairs as screw threads with pitch annotations, making it easier to compare relative thread coarseness and understand ratios.