Threading reference
Metric & Imperial Thread Pitch Chart
Check common metric and Unified inch thread pitches. Compare nominal designations, threads per inch (TPI), and converted pitch values. Use the drawing or component specification as the final authority for production.
Quick lookup
Find a thread designation
Enter a metric designation or Unified inch size, such as M8, M8x1.25, 1/4-20, or #10-32.
Spaces and x / × are treated as equivalent separators. A size-only metric query shows the listed pitches for that nominal size.
Metric Thread Pitch Chart
Common coarse sizes and selected fine pitches from the cited manufacturer chart. Metric TPI is not specified here.
| Designation | Series | Pitch (mm) | TPI | Data source |
|---|---|---|---|---|
| M3 × 0.50 | Metric coarse | 0.5000 | — | KIPP USA Thread Pitch ChartCross-check: OSG |
| M3 × 0.35 | Metric fine | 0.3500 | — | KIPP USA Thread Pitch Chart |
| M4 × 0.70 | Metric coarse | 0.7000 | — | KIPP USA Thread Pitch Chart |
| M4 × 0.50 | Metric fine | 0.5000 | — | KIPP USA Thread Pitch Chart |
| M5 × 0.80 | Metric coarse | 0.8000 | — | KIPP USA Thread Pitch Chart |
| M5 × 0.50 | Metric fine | 0.5000 | — | KIPP USA Thread Pitch Chart |
| M6 × 1.00 | Metric coarse | 1.0000 | — | KIPP USA Thread Pitch ChartCross-check: OSG |
| M6 × 0.75 | Metric fine | 0.7500 | — | KIPP USA Thread Pitch Chart |
| M8 × 1.25 | Metric coarse | 1.2500 | — | KIPP USA Thread Pitch ChartCross-check: OSG |
| M8 × 1.00 | Metric fine | 1.0000 | — | KIPP USA Thread Pitch Chart |
| M10 × 1.50 | Metric coarse | 1.5000 | — | KIPP USA Thread Pitch ChartCross-check: OSG |
| M10 × 1.25 | Metric fine | 1.2500 | — | KIPP USA Thread Pitch Chart |
| M12 × 1.75 | Metric coarse | 1.7500 | — | KIPP USA Thread Pitch ChartCross-check: OSG |
| M12 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M14 × 2.00 | Metric coarse | 2.0000 | — | KIPP USA Thread Pitch Chart |
| M14 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M16 × 2.00 | Metric coarse | 2.0000 | — | KIPP USA Thread Pitch Chart |
| M16 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M18 × 2.50 | Metric coarse | 2.5000 | — | KIPP USA Thread Pitch Chart |
| M18 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M20 × 2.50 | Metric coarse | 2.5000 | — | KIPP USA Thread Pitch Chart |
| M20 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M22 × 2.50 | Metric coarse | 2.5000 | — | KIPP USA Thread Pitch Chart |
| M22 × 1.50 | Metric fine | 1.5000 | — | KIPP USA Thread Pitch Chart |
| M24 × 3.00 | Metric coarse | 3.0000 | — | KIPP USA Thread Pitch Chart |
| M24 × 2.00 | Metric fine | 2.0000 | — | KIPP USA Thread Pitch Chart |
UNC Thread Pitch Chart
Selected Unified National Coarse designations. TPI is shown as published; millimeters per thread are calculated as 25.4 ÷ TPI.
UNF Thread Pitch Chart
Selected Unified National Fine designations. TPI is shown as published; millimeters per thread are calculated as 25.4 ÷ TPI.
Thread basics
What is thread pitch?
Thread pitch is the axial distance between adjacent thread crests. Metric designations state pitch directly in millimeters. Unified inch designations commonly state threads per inch (TPI), so one thread interval is calculated as 25.4 ÷ TPI millimeters.
Pitch (mm) = 25.4 ÷ TPI
Example: 24 TPI → 25.4 ÷ 24 ≈ 1.0583 mm.
TPI = 25.4 ÷ pitch (mm)
This is a unit conversion, not a designation of a metric thread series.
Metric pitch vs. TPI
M8 × 1.25 designates an 8 mm nominal diameter and 1.25 mm pitch. The chart shows that pitch as supplied by the source. The Unified tables show source-listed TPI and a four-decimal millimeter conversion.
UNC vs. UNF
UNC and UNF identify selected Unified coarse and fine series. A nominal diameter alone does not identify the thread series; confirm the complete designation, fit, and applicable standard.
Thread pitch is not a tap drill diameter
Pitch describes spacing between thread crests. It does not by itself determine a tap drill diameter. For a separate cutting-tap reference, see the Tap Drill Size Chart.
FAQ
How do I convert TPI to millimeters?
Divide 25.4 mm by the threads per inch. For example, 20 TPI converts to 1.2700 mm per thread interval.
Is M8 always 1.25 mm pitch?
No. M8 × 1.25 is the listed coarse pitch in this chart, and M8 × 1.00 is also listed. Confirm the full designation on the drawing or component.
What is the difference between UNC and UNF?
They are selected coarse and fine series within the Unified inch thread system. Use the complete thread designation to identify the intended series and pitch.
Can thread pitch alone choose a tap drill?
No. Pitch alone is not enough to select a tap drill. Confirm the thread standard, tap type, fit and the tap maker’s guidance.
How can I source taps from China?
Send the complete thread designation, tap type, workpiece material and quantity through the sourcing quote form. Suppliers must confirm product details and availability.
Technical references
Sources and verification
The metric selections are transcribed from KIPP’s published thread-pitch chart. Unified TPI values are checked against OSG’s thread table. Selected entries have an independent manufacturer cross-check. Values are reference data, not a substitute for the drawing or applicable standard.
- KIPP USA Thread Pitch Chart lists the metric coarse and fine selection and notes that metric products are supplied coarse unless otherwise specified.
- OSG Tap Drill Size & Pitch Diameter Limits, Vol. 3 (2024) contains Unified TPI entries and an ISO metric pitch table.
- Guhring M8 × 1.25 tap specification independently identifies this selected metric designation.
- Guhring 10-24 UNC thread mill specification, 1/4-20 UNC thread mill specification, and 1/2-13 UNC thread mill specification independently identify the listed sizes.
- Guhring 10-32 UNF thread mill specification, 1/4-28 UNF thread mill specification, and 5/16-24 UNF thread mill specification independently identify the listed sizes.
- ISO 261 defines the scope of the general-purpose metric thread plan; the public abstract does not expose the full numerical tables.
- ASME B1.1 covers Unified inch thread forms and series; the standard text is not reproduced here.
China tooling sourcing
Need taps or threading tools?
Send the thread designation, tap type, workpiece material and quantity. We can check sourcing options with Chinese manufacturers and distributors.
Request a Sourcing Quote