Calculator Inputs
Example Data Table
| Process | Gas | Nozzle (mm) | Wind (m/s) | Stickout (mm) | Joint | Recommended (L/min) | Recommended (CFH) |
|---|---|---|---|---|---|---|---|
| MIG/MAG | Argon/CO2 | 12 | 0.5 | 15 | Fillet | ~15.8 | ~33.5 |
| TIG | Argon | 9 | 0.0 | 10 | Butt | ~8.9 | ~18.9 |
| FCAW-G | CO2 | 14 | 1.2 | 20 | Open groove | ~26.0 | ~55.1 |
Examples are practical starting points; always confirm with weld quality checks.
Formula Used
This calculator uses a field-ready model that starts with a baseline flow from nozzle/cup diameter and process, then applies adjustment multipliers.
Recommended (L/min) = Baseline × Fgas × Fwind × Fjoint × Fposition × Fdistance × Fangle × Fsetup
- kprocess sets the baseline per process (starting point).
- Fwind increases flow for drafts, capped to avoid over-gassing.
- Fdistance increases flow for longer stickout/cup distance.
- Fsetup includes gas lens and nozzle extension effects.
How to Use This Calculator
- Select your welding process and shielding gas type.
- Enter nozzle/cup diameter and your typical stickout distance.
- Set expected wind or draft near the arc.
- Choose joint type, position, and torch angle.
- Click Calculate to see the recommended flow.
- Export results to CSV or PDF for job documentation.
- Verify with test beads and adjust if porosity appears.
Professional Article
Why Flow Rate Matters on Site
Shielding gas flow stabilizes the arc and blocks oxygen, nitrogen, and moisture from the molten pool. In construction welding, inconsistent flow is a common root cause of porosity, soot, and erratic bead shape, especially during field fit-up and repair work.
Typical Starting Ranges by Process
Practical shop baselines often land near 10–20 L/min for MIG/MAG, 6–14 L/min for TIG, and 12–25 L/min for gas-shielded flux-cored work. These are starting points; the correct setting depends on nozzle size, distance, drafts, and joint openness. For indoor structural steel, many crews target about 25-35 CFH for MIG and 15-25 CFH for TIG, then adjust after checking bead appearance and macro-etch samples.
Nozzle Diameter and Coverage Zone
Coverage increases with nozzle or cup diameter because the gas envelope must span a wider exit area. A 12 mm MIG nozzle generally needs more flow than a 10 mm nozzle, while a TIG #8 cup can run lower when a gas lens promotes laminar flow.
Wind, Fans, and Temporary Enclosures
Drafts can strip shielding quickly. A gentle 1.0–1.5 m/s airflow from wind or ventilation can double the defect risk unless you use screens, curtains, or temporary enclosures. Increasing flow helps, but physical shielding is usually more effective than extreme flow settings.
Stickout, Cup Distance, and Torch Angle
Long stickout or excessive cup-to-work distance lets ambient air mix into the stream. Keeping distance near 10–15 mm for many tasks reduces turbulence. Torch angles above 20–30° also thin the protective blanket, so tighter angles often allow lower, steadier flow.
Gas Type Effects in Real Welding
Gas choice influences density and stability. Pure CO2 can demand slightly higher flow than argon-rich mixes, and helium blends may need more volume to maintain coverage due to higher diffusion and different arc characteristics. Match the mix to procedure requirements and base metal.
Quality Clues: Under- and Over-Gassing
Too little flow often shows as pinholes, scattered porosity, or a dull, contaminated surface. Too much flow can create turbulence that actually pulls air into the stream, leading to similar defects plus wasted gas and noisy, unstable arc behavior. Listen and inspect test beads.
Documentation for Productivity and QA
Recording a repeatable setting improves productivity. Note process, gas mix, nozzle size, wind level, and distance on the job card. Use this calculator to capture a recommended range, then confirm with a short qualification run before full production welding. Track cylinder usage: lowering flow by only 2 L/min across a week can save hours of bottle changes and reduce downtime.
FAQs
What unit should I set on the flowmeter?
Use the unit printed on your regulator. Many meters show CFH, while some show L/min. This calculator displays both so you can match your gauge without guessing.
Can I just increase flow to fix porosity?
Sometimes, but not always. Porosity also comes from leaks, dirty base metal, moisture, and drafts. Solve airflow and cleanliness first, then fine-tune flow with test beads.
How does nozzle size change the recommended flow?
Larger nozzles need more volume to maintain the same gas velocity and coverage. If you change nozzle or cup size, recalculate and recheck bead quality.
When is a gas lens helpful?
In TIG, a gas lens straightens flow and improves coverage, especially with larger cups or longer stickout. It can allow slightly lower settings while keeping shielding stable.
What is over-gassing and why is it bad?
Excess flow can create turbulence that pulls air into the stream. You may see porosity, a harsh sound, or unstable arc behavior, plus higher gas consumption.
How do drafts affect outdoor welding?
Even light wind can break the shielding envelope. Use screens, tarps, or enclosures whenever possible. If exposure is unavoidable, document conditions and expect higher flow or alternative processes.
Should I record settings for each joint?
Yes. Logging process, gas, nozzle size, wind level, and distance makes results repeatable. It speeds setup on future welds and supports quality documentation.
Tune gas flow, protect puddle, and weld cleaner today.