Welding Shielding Gas Consumption & Cylinder Calculator
Shielding gas calculator for MIG and TIG: gas used per shift from flow rate and arc-on time, how long a cylinder lasts, cylinders needed for a job, gas cost per hour of arc time and per metre of weld, with allowances for pre/post-flow and leaks.
How it works
Gas per shift = flow × (hours × 60 × arc-on%) × (1 + overhead%); cylinder life = contents ÷ gas per shift; cost per arc hour = cylinder price ÷ (contents ÷ flow ÷ 60)
Shielding gas is bought by the cylinder but consumed by the minute of arc time, so the two numbers that matter are the torch flow rate and the operating factor — the share of the shift the arc is actually lit. Manual MIG welders spend most of their time fitting, tacking, grinding and repositioning, so a 30% arc-on figure is typical, while a robot cell may exceed 80%. Pre-flow, post-flow, purging and small leaks at fittings add 10–20% on top; hose and regulator leaks left overnight can quietly empty a cylinder. Measuring flow at the torch nozzle with a peashooter gauge rather than trusting the regulator ball, and turning flow down to the process minimum, are the two easiest savings.
Worked example
At 15 L/min for an 8-hour shift with 30% arc-on and 15% overhead a welder uses 2.48 m³ a day; a 9.4 m³ cylinder lasts 3.8 shifts (9.1 arc hours), so a 20-shift job needs 6 cylinders (~$390). Gas costs $7.16 per arc hour, about 40¢ per metre of weld at 30 cm/min.
Frequently asked questions
How many hours does a 300 ft³ cylinder last?
At 25 cfh (12 L/min) continuous flow, 300 ÷ 25 = 12 hours of arc time; at a 30% operating factor that is 40 shift-hours, about a week of manual MIG.
Is CO₂ measured the same way?
CO₂ cylinders are sold by weight (liquid); 1 kg of CO₂ gives about 0.54 m³ of gas, so a 30 kg cylinder holds about 16 m³. Draw rates above ~10 L/min can freeze the regulator without a heater.
Related calculators
Guidance values from published welding references (AWS D1.1 / EN 1011 style preheat bands, typical deposition efficiencies). Always follow the qualified welding procedure specification (WPS), the consumable data sheet and the machine nameplate; verify preheat and interpass temperatures with a contact thermometer or temperature crayon.