How to use this welding calculator
Pick a tab, choose your process and material, and type in your values. Results update instantly, and the Copy button puts them on your clipboard for a work order, quote or procedure sheet.
Weld settings: amperage, voltage, wire feed speed and gas
Welding amperage is driven mainly by material thickness. For MIG, flux-cored and TIG welding, about 35-45 amps per millimetre of thickness is a reliable starting point; aluminum needs more current than steel because it conducts heat away quickly. Voltage follows current (higher amperage needs higher voltage to keep the arc length stable), and wire feed speed sets the amperage on a constant-voltage MIG machine. The calculator picks wire diameter, tungsten size or electrode diameter, shielding gas and flow rate to match.
Heat input
Heat input is the energy delivered to the joint per unit length of weld. Too little causes lack of fusion and fast cooling; too much softens the heat-affected zone and can ruin the toughness of high-strength, duplex and stainless steels. Many codes and WPSs specify a maximum in kJ/mm or kJ/in. Enter voltage, current and travel speed, or enter a target heat input and the calculator gives the travel speed that achieves it.
Filler metal weight and welding cost
The cost tab computes the weld metal cross-section for fillet, square butt, single V, double V and single bevel joints, adds reinforcement, then converts volume to weight using material density. Dividing by deposition efficiency shows how much wire or electrode you actually need to buy. Filler, shielding gas, electricity and labor (using your operating factor) are added up into a total and a cost per metre or foot.
Carbon equivalent and preheat
Carbon equivalent predicts how prone a steel is to hardening and cracking after welding. The tool reports IIW CE and Pcm from the chemical composition and gives a Séférian preheat estimate that accounts for plate thickness. Choose a preset such as S355 or 4130, or type in the values from your mill certificate.
Duty cycle
Duty cycle tells you how long a welder can run before it must cool. Enter the rating from the machine's nameplate and the current you plan to use to see the allowed weld time per ten minutes and the continuous 100% current.
Frequently asked questions
How do I calculate welding amperage?
A common rule of thumb for MIG and TIG welding is about 1 amp per 0.001 inch (roughly 40 A per millimetre) of material thickness. Stick welding amperage is set mainly by electrode diameter. The Weld settings tab turns this into a starting amperage range, voltage, wire size and gas flow for your process and material.
How is welding heat input calculated?
Heat input (kJ/mm) = thermal efficiency × voltage × current × 60 ÷ (travel speed in mm/min × 1000). Efficiency is 0.8 for MIG, flux-cored and stick, 0.6 for TIG and 1.0 for submerged arc welding, according to EN 1011-1.
How much filler metal do I need for a weld?
Multiply the weld cross-section area by the weld length to get the volume, then multiply by the metal density (7.85 g/cm³ for steel) to get deposited weight. Divide by the deposition efficiency (about 95% for solid MIG wire, 85% for flux-cored, 60% for stick) to get the filler you must buy.
What is carbon equivalent and why does it matter?
Carbon equivalent (CE) expresses how the alloying elements in steel affect hardenability. The higher the CE, the greater the risk of hydrogen cracking in the heat-affected zone, and the more likely you need preheat. An IIW CE below 0.35 is generally easy to weld.
What does duty cycle mean on a welder?
Duty cycle is the percentage of a 10-minute period a welder can run at a given current without overheating. A 250 A machine rated at 60% can weld 6 minutes out of every 10 at 250 A. At lower currents the duty cycle rises with the square of the current ratio.
Are the results safe to use for code work?
No. The calculator gives engineering estimates for planning, training and quoting. For structural or pressure work always follow your qualified welding procedure specification (WPS), the applicable code such as AWS D1.1 or ISO 15614, and the consumable manufacturer's data.
More welding tools
- Fillet Weld Strength Calculator - Throat, allowable load, safety factor and required leg size per AWS D1.1.
- Shielding Gas Selector - Pick the right gas blend for your process, material and priority.
- Welding Electrode Selector - Compare stick electrodes by position, power source and application, with amp ranges.
- Welding Amperage Chart - Settings tables by material thickness for every process, in mm and inches.