Model nugget strength using factors for material, temperature, safety, and quality needs. Get weld count, spacing guidance, utilization, and exportable summaries for reports today.
| Case | Mode | Nugget diameter | Thickness | Material UTS | Welds | Safety factor | Design total capacity |
|---|---|---|---|---|---|---|---|
| A | Shear | 6 mm | 2 mm | 400 MPa | 6 | 2.0 | ~20–30 kN |
| B | Tension | 8 mm | 3 mm | 515 MPa | 4 | 2.5 | ~18–28 kN |
| C | Peel | 5 mm | 1.6 mm | 310 MPa | 8 | 2.0 | ~8–14 kN |
This calculator estimates a weld nugget’s load capacity using a stress-on-area approach.
k = efficiency × joint factor × temperature factor × mode factor. Peel cases use a lower mode factor to reflect higher sensitivity to eccentricity.
Spot welds appear in light-gauge framing, duct supports, equipment enclosures, and sheet-metal liners. They are fast to produce, but strength depends on nugget formation, fit-up, and load path. Use this calculator to compare options before finalizing site procedures.
The key geometric input is nugget diameter d. The effective area is A = (π/4)·d², so capacity scales with diameter squared. Small increases in d can raise strength significantly. Track measured nuggets when inspection data is available.
Strength is estimated from ultimate tensile strength (UTS). Typical values include mild steels near 400 MPa, higher-strength steels near 600 MPa, and common aluminum alloys near 310 MPa. Select a preset or enter a verified UTS. The tool converts MPa/ksi automatically.
Performance differs in shear, direct tension, and peel. This calculator uses practical estimates: shear capacity is tied to about 0.60·UTS, while tension uses about 0.80·UTS. Peel is reduced further to reflect eccentricity, prying, and separation sensitivity.
Efficiency represents scatter from surface condition, electrode wear, access, and inspection acceptance. For controlled production, 0.85–0.95 is often reasonable. For variable field conditions, 0.75–0.90 may be safer. Adjust efficiency to model uncertainty without changing geometry inputs.
The tool estimates nominal capacity per weld, then divides by the safety factor to obtain design capacity. Safety factors of 2.0–3.0 are common when loads and quality are uncertain. Use higher values for dynamic effects, fatigue risk, or limited inspection coverage.
Closely spaced welds can interact and weaken sheet material, while small edge distances promote tear-out. As a rule-of-thumb, the tool suggests pitch ≥ max(4d, 10t) and edge distance ≥ max(2d, 5t). Confirm detailing requirements with project specifications and engineering review.
Use the CSV and PDF outputs to document inputs, assumptions, and utilization. For critical connections, confirm the procedure through qualification and representative testing, and align acceptance criteria with inspection plans. Final design should follow applicable standards and the engineer-of-record’s requirements.
Saved calculations support QA/QC closeout packages and help communicate design intent to supervisors and inspectors clearly.
1) Which unit system should I use?
Use the same unit system as your drawings and load data. The calculator converts internally, so results stay consistent when switching between metric and imperial inputs.
2) When should I enter a custom UTS?
Use custom UTS when material certificates, specifications, or testing provide a better value than presets. Enter MPa for metric or ksi for imperial.
3) Why does peel show lower capacity?
Peel introduces eccentric loading and prying, which promotes early separation. The tool applies a conservative mode factor to reflect that reduced repeatability.
4) How do I pick the efficiency factor?
Start near 0.85 for controlled production. Reduce it for dirty surfaces, difficult access, inconsistent fit-up, or limited inspection. Higher confidence allows a higher efficiency.
5) What does “required welds” mean?
It is the minimum weld count needed to resist the applied load using the calculated design capacity per weld. If it exceeds installed welds, increase weld size or count.
6) Are the pitch and edge distances mandatory?
No. They are rule-of-thumb starting points to reduce interaction and tear-out risk. Always confirm detailing requirements with project specifications and engineering review.
7) What’s included in the PDF and CSV exports?
Both exports include all input parameters and the computed outputs, making it easier to store calculation records and share them with supervisors, QA/QC, or reviewers.
Use these results to plan safer weld schedules today.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.