Welding wire consumption per meter is the number you need before you order a spool or quote a job. The good news is that it comes from one short formula, and for fillet welds you can read it straight from a chart. This guide puts the chart first, then shows how it was built so you can adapt it to your own joint.
Short answer
Wire needed = weld metal weight ÷ deposition efficiency. For a 6 mm equal-leg fillet weld in steel, the weld metal is about 141 g per meter. At 95% efficiency that means about 149 g of wire per meter of weld. This is the theoretical weld size, so real welds with extra weld metal use more.
Last reviewed: October 2026. Efficiency figures are as published on the linked page in October 2026. Check the current version before you rely on them.
The Quick Chart: Wire per Meter of Fillet Weld
This chart is for an equal-leg fillet weld in steel, with a flat face and no extra reinforcement. The three efficiency columns come from the process figures in the section "What Changes the Number" below. Every number here is calculated for this guide, not copied from a table.
| Leg size | Weld area | Weld metal per meter | Wire per meter at 95% | Wire per meter at 87% | Wire per meter at 65% |
|---|---|---|---|---|---|
| 3 mm | 4.5 mm² | 35 g | 37 g | 41 g | 54 g |
| 4 mm | 8.0 mm² | 63 g | 66 g | 72 g | 97 g |
| 5 mm | 12.5 mm² | 98 g | 103 g | 113 g | 151 g |
| 6 mm | 18.0 mm² | 141 g | 149 g | 162 g | 217 g |
| 8 mm | 32.0 mm² | 251 g | 264 g | 289 g | 386 g |
| 10 mm | 50.0 mm² | 392 g | 413 g | 451 g | 604 g |
| 12 mm | 72.0 mm² | 565 g | 595 g | 650 g | 870 g |
Notice how fast the numbers grow. Doubling the leg from 5 mm to 10 mm does not double the wire. It multiplies it by four, because the weld area depends on the square of the leg.
How the Chart Was Built
TWI describes the method: find the cross-sectional area of the weld, multiply by the length to get volume, then multiply by the density of the alloy. It also gives the area of an equal-leg fillet weld as half the square of the leg length. You can read the details in TWI's guide to calculating weld volume and weight.
Weld metal per meter (g) = weld area × 7.85
Wire per meter (g) = weld metal per meter ÷ deposition efficiency
The 7.85 works out neatly. One square millimeter of area over one meter of length is 1 cm³, and steel at 7.85 g/cm³ weighs 7.85 g. TWI's density table lists 7.86 g/cm³ for a 0.25% carbon steel, so the two values are within about 0.1%. Alloying elements can change density, so use the right value for other metals.
Passes do not change the weld metal. If a joint is built in three passes, the three passes together still fill the same area. Passes matter for time, not for the weld metal quantity.
What Changes the Number: Deposition Efficiency
Not all the wire you feed ends up in the weld. The Welder defines deposition efficiency as the weld metal deposited divided by the filler metal consumed. It lists these typical values:
| Process | Deposition efficiency (published) | Used in the chart above |
|---|---|---|
| GMAW (solid and metal-cored wire) | 92% to 98% | 95%, a value inside the range |
| FCAW | about 87% | 87% |
| SMAW (stick) | about 65% | 65% |
| GTAW (with filler) and SAW | about 99% | not used |
For the same 6 mm fillet weld, the wire needed per meter goes from about 143 g at 99% to about 154 g at 92%, then 162 g at 87% and 217 g at 65%. Between 99% and 65%, that is roughly 50% more wire, so use the efficiency for your own process, and your own measured value if you have one.
Turn Grams into Meters of Wire on a Spool
Spools are often sold by weight, but you may also want the length. For solid steel wire, the weight per meter is the cross-section area of the wire times 7.85.
| Solid steel wire diameter | Weight per meter | Length per kg |
|---|---|---|
| 0.8 mm | 3.95 g | 253 m |
| 0.9 mm | 4.99 g | 200 m |
| 1.0 mm | 6.17 g | 162 m |
| 1.2 mm | 8.88 g | 113 m |
| 1.6 mm | 15.78 g | 63 m |
A Worked Order: 40 m of 6 mm Fillet Weld
Say you need 40 m of 6 mm equal-leg fillet weld in steel with a GMAW solid wire. These numbers are an example, not a quote.
| Step | Calculation | Result |
|---|---|---|
| 1. Weld area | 6 × 6 ÷ 2 | 18 mm² |
| 2. Weld metal per meter | 18 × 7.85 | 141.3 g |
| 3. Weld metal for 40 m | 141.3 g × 40 | 5.65 kg |
| 4. Wire at 95% efficiency | 5.65 ÷ 0.95 | 5.95 kg |
| 5. Length of 1.0 mm wire | 5.95 kg × 162.2 m/kg | about 965 m |
| 6. Share of a 15 kg spool | 5.95 ÷ 15 | about 0.4 spool |
The 15 kg spool size is only an example. Use the spool weight your supplier sells.
What the Chart Does Not Include
The chart gives the theoretical amount for the drawing size. TWI points out that welders seldom deposit exactly the size on the drawing, and that extra weld metal on the weld face changes the quantity used. So treat the chart as a clean baseline.
- Extra weld face (convexity): adds weld metal on top of the theoretical area.
- Different joint types: butt welds have a different area, including root gap, groove angle and reinforcement.
- Wire that never reaches the weld: for example wire cut off at the end of a spool. Add an allowance based on your own shop experience.
- Other metals: change the density, and the efficiency for the process.
Questions People Ask About Welding Wire Consumption per Meter
How much wire does 1 meter of 6 mm fillet weld use?
The theoretical weld metal is about 141 g per meter in steel. At 95% deposition efficiency, that means about 149 g of wire. At 87% it is about 162 g, and at 65% about 217 g.
What is the formula for welding wire consumption?
Weld area × length × density gives the weld metal weight. Divide that by the deposition efficiency to get the wire weight. For an equal-leg fillet weld, the area is half the square of the leg.
What is deposition efficiency?
It is the weld metal deposited divided by the filler metal consumed. The Welder lists about 65% for stick welding, about 87% for flux-cored, 92% to 98% for GMAW solid and metal-cored wire, and about 99% for TIG and submerged arc.
Do more passes use more wire?
Not by themselves. The weld metal depends on the cross-section area of the finished weld, however many passes it takes to fill it.
Why did the real job use more wire than the chart?
The chart uses the drawing size. TWI notes that welders seldom deposit exactly that size, and that extra metal on the weld face changes the quantity. A real efficiency that is lower than the typical value also raises the wire used.
Can I use this chart for stainless steel or aluminum?
The method is the same, but the density is different. TWI's table lists about 7.92 g/cm³ for 304 stainless steel and 2.70 g/cm³ for aluminium, so the weight per meter changes. Use the efficiency for your process and the right density for your wire.
Summary
Welding wire consumption per meter is the weld metal weight divided by the deposition efficiency. For a fillet weld, the weld metal comes from half the leg squared, times the density. Use the chart for a quick baseline, then adjust for your process efficiency and any extra weld metal on the real joint.
This guide is for general information and estimating. Real welds vary with joint fit-up, welder technique, process settings and material, and the published efficiency figures may change. Please check quantities against your approved welding procedure and with your supplier before you order or quote a job. Links to other websites are provided for reference only, and BytePriva is not responsible for their content. Read our full disclaimer.
Sources and Further Reading
- TWI: Calculating Weld Volume and Weight. Fillet weld area, weight as volume times density, and alloy densities.
- The Welder: Deposition rate, deposition efficiency and production output. Definition of deposition efficiency and typical values by process.
Calculate Your Wire Consumption
BytePriva's Welding Wire Consumption Calculator covers fillet welds and square and V-groove butt welds. You enter the joint dimensions, the filler material, the welding process and the deposition efficiency. It shows the weld cross-section area, the weld metal weight, the wire needed, and, if you add wire diameter and spool weight, the wire length and spool count. If you also add travel speed, labor rate and wire price, it gives time and cost.
Its page says the density and efficiency values are starting points that you can edit, and that passes affect time but not the metal quantity. Check the result against your approved welding procedure before you order.
Tool link: https://bytepriva.com/welding-wire-consumption-calculator/