A rule widely used in sheet-metal and aircraft work says the rivet diameter should be about three times the thickness of the thickest sheet. The shank must be longer than the grip so there is enough material to form the shop head: about 1.5 diameters for a button (round) head, more for pressure-vessel work, and only half a diameter for a countersunk head.
How to use the Rivet Size Calculator
- Head and application
- Thickest plate
- Total grip (all plates)
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the head shape and application, enter the thickness of the thickest plate and the total thickness of all plates (the grip).
Tips for an accurate estimate
- Keep units consistent – the calculator handles conversions, but check every field’s unit before reading a result.
- Use values from standards, data sheets or test pieces whenever you have them; typical values are only a starting point.
- Apply appropriate safety factors and have structural, electrical and pressure work checked by a qualified professional.
- Record the inputs you used so the calculation can be reviewed later.
Common mistakes to avoid
- Confusing diameter and radius, or nominal and actual sizes.
- Using allowable stresses and ultimate strengths interchangeably.
- Treating rule-of-thumb results as a substitute for code tables or an engineered design.
Inputs explained
| Field | What to enter |
|---|---|
| Head and application | Choose one: Button head – general construction, Button head – pressure vessel / boiler, Countersunk head |
| Thickest plate | Units: mm, in |
| Total grip (all plates) | Units: mm, in |
What each result means
- Minimum diameter = 3×[Thickest plate]
- Standard size (next 1/32 in) = ceil([Minimum diameter]÷(0.0254÷32) – 0.000001)×0.0254÷32
- Standard size (fraction) = [Standard size (next 1÷32 in)]
- Metric size (next 0.5 mm) = ceil([Minimum diameter]÷0.0005 – 0.000001)×0.0005
- Rivet length = [Total grip (all plates)] + [Allowance factor c]×[Standard size (next 1÷32 in)]
Example values
How the main result changes when Thickest plate changes and everything else stays at the example values above:
| Thickest plate (mm) | Standard size (next 1/32 in) (in) |
|---|---|
| 0.8 | 0.125 |
| 1.2 | 0.1563 |
| 1.6 | 0.2188 |
| 2 | 0.25 |
| 2.4 | 0.3125 |
| 3.2 | 0.4063 |
Formula
D_min = 3 × t_maxA = c × D (c = 1.5 / 1.6 button head general, 1.7 / 1.8 boiler, 0.5 countersunk)L = S + A, where S is the total grip (all plates)Worked example
Inputs — Head and application: Button head – general construction; Thickest plate: 1.6 mm; Total grip (all plates): 3.2 mm.
Results — Minimum diameter = 4.8 mm; Standard size (next 1/32 in) = 0.2188 in; Standard size (fraction) = 7/32; Metric size (next 0.5 mm) = 5 mm; Allowance factor c = 1.5; Rivet length = 0.454 in.
Frequently asked questions
How do I choose a rivet diameter?
Use about three times the thickness of the thickest sheet, rounded up to a standard size.
How long should a rivet be?
Grip plus 1.5 × diameter for a round shop head; grip plus about 0.5 × diameter for countersunk.
What is the grip?
The total thickness of all the material being joined.
What formula does the Rivet Size Calculator use?
D_min = 3 × t_max.