Rivet Size Calculator
Estimate a practical solid-rivet diameter and shank length from the thickness of two joined sheets.
Joint inputs
Recommended dimensions
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| Thickest sheet | max(2.00, 3.00) | 3.00 mm |
| Rivet diameter | 3 × 3.00 | 9.00 mm |
| Total stack | 2.00 + 3.00 | 5.00 mm |
| Shank length | 5.00 + 1.5 × 9.00 | 18.50 mm |
How to use this rivet size calculator
What this calculator does
This calculator estimates four dimensions for a conventional solid-rivet joint: a minimum practical shank diameter, the total grip or material stack, an approximate shank length, and nominal formed shop-head dimensions. It applies the widely used preliminary rule that rivet diameter is about three times the thickness of the thickest sheet. It then adds a forming allowance of 1.5 rivet diameters to the total sheet thickness to estimate shank length. The result is useful for initial selection and workshop planning, but it does not replace a load analysis, approved repair data, manufacturer instructions, or a certified engineering drawing.
When to use it
Use it when planning a lap joint between two sheets, checking whether an existing rivet is long enough to form a shop head, comparing metric and inch stock, or preparing a preliminary bill of materials before choosing the next available standard rivet size. NASA's Fastener Design Manual provides broader design guidance on rivets, materials, fatigue, corrosion, and joint selection.
How to calculate
- The calculator opens with a complete demonstration: Sheet 1 thickness is 2 mm and Sheet 2 thickness is 3 mm. Its Excel workbook is ready immediately.
- Replace Sheet 1 thickness and Sheet 2 thickness with the actual positive sheet values. Use a period as the decimal separator.
- Choose Measurement unit. Switching between millimeters and inches converts both entered values rather than merely relabeling them.
- Read Recommended rivet diameter first, then confirm Required shank length. Use the breakdown table to audit each formula step.
- Select Download Excel to export the current typed inputs and results to a validated OOXML workbook. Reset clears the demonstration data and disables export until both required thicknesses are complete and valid again.
Input guide
Sheet 1 thickness is required and accepts a positive decimal in the selected unit; 2 mm is the startup example. A larger value raises the total stack and may also raise the recommended diameter if it becomes the thicker sheet. Do not enter a material width, gauge number, or mixed unit. Sheet 2 thickness follows the same rules; the startup value is 3 mm. Because the diameter rule uses the thicker sheet, increasing the thinner sheet affects length but not diameter until it exceeds the other sheet. Measurement unit is a required choice between millimeters and inches. It converts current values using 25.4 mm per inch; do not manually convert and then also change the selector.
Output guide
Recommended rivet diameter is the three-times-thickest-sheet estimate. Total material thickness is the exact sum of both input sheets. Required shank length is the total stack plus 1.5 diameters of allowance for forming the shop head. Shop-head diameter target is 1.5 times shank diameter, while Shop-head height target is 0.5 times shank diameter. These are dimensional estimates, not proof of joint strength. A high value simply reflects thicker material; a zero or missing result means the inputs are incomplete or invalid.
Worked example
With 2.00 mm and 3.00 mm sheets, the thicker sheet is 3.00 mm. The estimated diameter is 3 × 3.00 = 9.00 mm. The material stack is 2.00 + 3.00 = 5.00 mm. Adding the forming allowance gives 5.00 + 1.5 × 9.00 = 18.50 mm, matching the first-open result and workbook. In practice, choose a standard diameter and length that meet or exceed the minimum while respecting the approved joint specification. The FAA's Aviation Maintenance Technician Handbook – Airframe is an authoritative source for aircraft sheet-metal practices.
Formula and interpretation
The calculation uses D = 3t, where t is the thickest individual sheet, followed by L = T + 1.5D, where T is the combined material thickness. The diameter formula is deliberately based on the thickest sheet rather than the total stack, because local bearing and deformation around the hole depend strongly on each sheet's thickness. The length formula reserves enough protruding shank to form the driven head. Atlas Copco describes the same three-times-thickness selection rule and 1.5D allowance.
Common mistakes
- Using total stack thickness in the diameter rule instead of the thickest individual sheet.
- Forgetting the 1.5D protrusion allowance and choosing a rivet whose shank only equals the material stack.
- Rounding down to a smaller stock size. Preliminary minimums are normally rounded up, subject to the specification.
- Mixing inches and millimeters. Use the unit selector so every displayed and exported value stays consistent.
- Treating the result as a structural approval. The NASA manual emphasizes that fastener selection involves fatigue, vibration, corrosion, temperature, and other design factors beyond geometry.