Weld Heat Input Calculator - AWS D1.1 & ASME IX Style Heat Input
Calculate heat input in kJ/inch from voltage, amperage, and travel speed per welding code requirements
Free weld heat input calculator for structural, pressure vessel, and pipeline welding review. The app computes the common arc-energy formula: Heat Input (kJ/in) = (Voltage × Amperage × 60) / (Travel Speed × 1000). Enter welding parameters - arc voltage, welding current, and travel speed in inches per minute - to produce a review value for comparison against the governing WPS/PQR, code edition, contract, and welding-engineering requirements. The app includes broad process rows for SMAW, GMAW (MIG), FCAW, GTAW (TIG), and SAW, but process efficiency factors and material screening thresholds are disclosed source gaps. Pulsed or waveform-controlled GMAW may require instantaneous energy/power methods outside this calculator.
Check simplified fillet weld-metal load with source warnings
Fillet Weld Strength Calculator →Check shielding gas consumption and refill cost
MIG/TIG Gas Consumption Estimator →Calculate total shop power for welding stations
Machine Shop Power Calculator →Select the right weld joint prep geometry before you strike an arc
Weld Joint Prep Calculator →How It Works
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Select Welding Process
Choose your welding process: SMAW (stick), GMAW (MIG), FCAW (flux-core), GTAW (TIG), or SAW (submerged arc). The process determines the thermal efficiency factor if your code requires net heat input rather than arc heat input.
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Enter Arc Voltage
Input the measured arc voltage during welding. This is not the machine's set voltage - it is the actual voltage measured at the arc during welding. For SMAW, typical values are 20-30V. For GMAW spray transfer, 26-34V. For GTAW, 10-18V.
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Enter Welding Current
Input the measured welding amperage. For constant-current processes (SMAW, GTAW), this is set on the machine. For constant-voltage processes (GMAW, FCAW), measure it with a clamp-on ammeter during welding because actual amps vary with wire feed speed and stickout.
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Enter Travel Speed
Input travel speed in inches per minute. Measure this in the field by timing a known weld length. For multi-pass welds, measure each pass separately as travel speed often differs between root, fill, and cap passes.
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Review Heat Input Against the WPS
Use the calculated heat input in kJ/inch as a review value, then compare it against the qualified range and essential variables in the governing WPS/PQR and code edition.
Built For
- Welding inspectors verifying that production welds meet WPS heat input limits
- Welding engineers preparing procedure qualification records for AWS D1.1 or ASME IX
- Pipeline welders preparing heat-input logs for review against the applicable procedure and project requirements
- Fabrication shops training welders on the relationship between parameters and heat input
- QA/QC departments auditing welder parameter logs against qualified WPS ranges
Assumptions
- Heat input formula uses H = (V x A x 60) / (S x 1000), where V is voltage, A is amperage, and S is travel speed in inches per minute.
- Arc efficiency factor is a local screening prompt: SMAW 0.80, GMAW 0.85, GTAW 0.70, FCAW 0.85, SAW 0.95; governing factors come from the WPS/code/source review.
- Welding parameters (voltage, amperage, travel speed) are steady-state values, not peak or transient readings.
- Travel speed is linear and does not account for weaving or oscillation patterns.
Limitations
- Does not calculate cooling rate (t8/5) or predict HAZ hardness from the heat input value.
- Preheat and interpass temperature effects on metallurgy are not modeled beyond flagging code limits.
- Multi-pass weld cumulative heat input and thermal cycling effects are not analyzed.
- Does not determine whether the WPS essential variable ranges are met for a specific code or standard.
References
- AWS D1.1 - Structural Welding Code, Steel (heat input limits and essential variables)
- ASME BPVC Section IX - Welding, Brazing, and Fusing Qualifications (essential variable ranges)
- AWS Welding Handbook, Volume 1 - Welding Science and Technology (arc energy and heat flow)
- ISO/TR 18491 - Guidelines for measurement of welding energies (arc thermal efficiency source pointer)
Frequently Asked Questions
Learn More
How to Read AWS Welding Electrode Numbers
What the digits and letters on a welding rod or wire mean: tensile strength, welding position, the last two digits for coating and current, low-hydrogen status, and the difference between E7018, ER70S-6, and E71T-1.
Why Weld Heat Input Matters More Than You Think
What heat input actually controls in the weld zone, cooling rate metallurgy for non-metallurgists, AWS D1.1 requirements, and how to measure travel speed accurately.
Fillet Weld Strength Planning
Effective throat vs leg size, AWS D1.1 allowable stresses, the cost of overwelding, base metal shear failure, and why increasing weld length beats increasing weld size.
Where Your Welding Gas Money Actually Goes
Shielding-gas planning limits, flow-rate source gaps, cylinder vs bulk quote checks, leak checks, and WPS review boundaries.
AWS D1.1 Weld Joint Prep Guide: Groove Geometry, Filler Metal & Prequalified Joints
How to select and prepare CJP and PJP groove welds per AWS D1.1. Covers prequalified joints, groove parameters, filler metal estimation, backing bars, and joint prep methods.
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