Input Parameters
Calculated Thread Dimensions
| Parameter | Symbol | Value | Notes |
|---|---|---|---|
| Enter thread data and press “Calculate dimensions” to see results. | |||
Example Metric Thread Sizes
Typical coarse-pitch ISO metric threads are shown below as quick reference for common mechanical design work.
| Thread | Major diameter (mm) | Pitch (mm) | Typical application |
|---|---|---|---|
| M3 × 0.5 | 3.00 | 0.50 | Small fasteners in electronics and light assemblies. |
| M4 × 0.7 | 4.00 | 0.70 | General-purpose machine screws and cover plates. |
| M6 × 1.0 | 6.00 | 1.00 | Automotive brackets, light structural connections. |
| M8 × 1.25 | 8.00 | 1.25 | Medium-duty joints and machinery housings. |
| M10 × 1.5 | 10.00 | 1.50 | Engine components and structural steel bolting. |
| M12 × 1.75 | 12.00 | 1.75 | Heavy brackets, flanges, and frame bolts. |
| M16 × 2.0 | 16.00 | 2.00 | Large structural joints and anchor bolts. |
Formula Used
The calculator is based on ISO metric 60° thread geometry. For a given pitch P (mm) and major diameter d or D, the following relationships are applied:
- Basic triangle height:
H = 0.8660254 × P - External radial thread depth:
he = 0.61343 × P - Internal radial thread depth:
hi = 0.54127 × P - External minor diameter:
d3 = d − 2 × he - Internal minor diameter:
D1 = D − 2 × hi - Pitch diameter (both external and internal):
d2, D2 = d, D − 0.64952 × P - Lead for multi-start threads:
L = P × number of starts - Lead angle at pitch diameter:
tan λ = L / (π × d2) - Approximate tensile stress area (external):
As ≈ π/4 × (d2 − 0.9382 × P)2
These expressions approximate commonly-used ISO metric thread proportions and are suitable for preliminary design, checking, and documentation purposes. Always confirm against official standards for safety-critical components.
How to Use This Calculator
- Select whether you want to use a standard ISO metric thread or custom geometry.
- For standard threads, choose the required designation from the list, including coarse or fine series.
- For custom threads, type the major diameter and pitch values in millimetres.
- Choose whether the thread is external (bolt/screw) or internal (nut/hole).
- Specify thread direction, number of starts, decimal places, and optional inch display.
- Press Calculate dimensions to populate the table with calculated values.
- Use the CSV or PDF download buttons to archive the results for drawings or reports.
Always confirm final dimensions and tolerances against the relevant ISO metric standard and class of fit before manufacturing or inspection.
Metric Threads in Structural Steel Connections
Bolts with ISO metric threads are widely used in column bases, splice plates, and roof truss seats. This calculator lets you confirm pitch, minor diameter, and lead before detailing gusset connections or checking bolt groups in structural drawings.
For roof slab work you can pair thread checks with the Concrete Roof Paver Load Calculator when verifying bearing, slip resistance, and anchorage requirements.
Fasteners for Stainless Steel Assemblies
Curtain wall brackets, facade supports, and exposed architectural elements often use stainless steel bolts and anchors. The metric profile stays the same, but tensile stress area and corrosion resistance drive strength calculations and material selection.
You can estimate piece weights with the Stainless Steel Weight Calculator while sizing bolts to carry combined dead and wind actions safely.
Anchoring Roof and Shingle Systems
Thread dimensions influence clamp force, pull-out resistance, and slip in roof fixing systems. Coarse threads suit timber blocking and anchors in soft materials, while fine threads improve adjustment accuracy in metal purlins and clip angles.
When estimating cover, waste, and fixing requirements, combine these results with a shingle roof estimating tool for a complete roof design workflow.
Choosing Coarse or Fine Pitch on Site
Coarse-pitch metric threads resist damage, assemble quickly, and are preferred for general construction bolts. Fine-pitch threads offer higher tensile capacity for a given diameter and finer adjustment but demand cleaner threads and more precise fabrication, especially on heavily galvanized or painted components.
Checking Lead, Pitch, and Embedment Lengths
Multi-start threads are sometimes used on adjustment screws, jacks, and heavy equipment foundations. The lead from this calculator helps you confirm how far a nut or leveling device moves per revolution when setting machinery pads or adjusting shims under baseplates.
Exporting Data for Construction Documentation
Use the CSV download to move thread dimensions into connection schedules, bolt lists, or fabrication spreadsheets. The PDF export quickly documents critical diameters and lead angles for method statements, inspection checklists, or site instructions without manually copying values from design sketches.
Frequently Asked Questions
1. What standards does this metric thread calculator follow?
The formulas are based on the basic ISO metric 60° profile and common handbooks. They provide approximate geometric values only. Always confirm tolerances, classes of fit, and material requirements using the official ISO standards relevant to your project.
2. Can I use these results directly for structural anchor design?
No. The tool gives geometric sizes, lead, and approximate stress area only. Structural design still requires code checks for pull-out, shear, combined actions, edge distances, pry forces, and safety factors using applicable building design codes.
3. How should I choose between coarse and fine pitch threads?
Coarse threads suit most construction bolts because they assemble quickly and tolerate minor damage. Fine threads are helpful when you need precise adjustment, limited space, or slightly higher tensile capacity, but they demand cleaner, better protected threads on site.
4. Why can I toggle inch equivalents for the dimensions?
Many construction drawings and specifications mix metric and imperial units. Showing both millimetres and inches helps communicate thread sizes to suppliers, mixed-unit design teams, and fabricators while keeping calculations and governing equations in a consistent metric basis.
5. Can this calculator help when checking roof paver fixings?
Yes. You can confirm thread depth, minor diameter, and lead for bolts that clamp pedestal heads or restraint plates. Combine this with the Concrete Roof Paver Load Calculator when reviewing bearing, slip, and service load combinations.
6. Why is my calculated lead angle very small?
Metric structural bolts usually have relatively fine leads compared with their diameter, so the helix is shallow. The calculator reports lead angle at pitch diameter. Small angles are normal and still provide adequate clamp force and thread engagement.
7. Does this tool include tolerances and fits for bolts and nuts?
No. The tool reports basic sizes only. Tolerance positions, classes of fit, and plating allowances must be checked separately against ISO tolerance tables, product standards, or manufacturer data sheets for the specific fasteners being specified.