Weld Deposition Rate Calculator
Work out deposition rate, the weld metal a joint needs, arc time and consumable cost - with the deposition efficiency that separates wire bought from weld deposited.
How to use this calculator
- 1Enter the weld size from the drawing symbol, not from what is usually run - over-welding is the most common and most expensive habit there is.
- 2Use the operating factor honestly. Twenty to thirty percent is normal for manual work and it dominates the elapsed time.
- 3Include a labour rate. It is typically several times the consumable cost and it is what actually decides between processes.
- 4Compare consumables on cost per foot of finished weld rather than on price per pound.
How the calculation works
Wire weight per inch = pi (d/2)^2 x density
Deposition rate (lb/hr) = wire weight per inch x wire feed (in/min) x 60 x deposition efficiency
Fillet section = leg^2 / 2, plus about 10% for the convex face
Weld metal per foot = section x 12 x density
Consumable to buy = weld metal / deposition efficiency- Deposition efficiency
- The share of consumable that ends up as weld. About 95% for solid MIG wire, 85% flux-cored, 65% stick
- Operating factor
- Arc-on time as a fraction of the working day. 20-30% for manual work, 60%+ mechanised
- leg^2 / 2
- The section of a fillet is a right triangle with two equal legs
The derived deposition figures match the published ones: 0.045 in wire at 300 in/min gives 8.1 lb/hr against the 8 the trade quotes, and moving from 0.035 to 0.045 at the same feed raises it 65%, which is also the published step.
The fillet figures check out the same way: a quarter-inch fillet at leg squared over two is 0.03125 sq in, which is 0.106 lb per foot in steel - the number in every estimating table.
Deposition rate rises slightly faster than current because of resistive heating along the electrode stickout, so a long stickout deposits more at the same amperage. The relationship used here is the first-order one.
Worked example
A hundred feet of quarter-inch fillet in MIG
- 1.A 1/4 in fillet is leg squared over two: 0.03125 sq in, plus 10% for the convex face.
- 2.That is 0.1170 lb per foot in steel, so 100 ft needs 11.7 lb of weld metal.
- 3.0.035 wire at 300 in/min consumes 4.91 lb/hr, and solid wire deposits about 95% of it - so 4.67 lb/hr of actual weld.
- 4.Two and a half hours of arc, which at a 30% operating factor is over eight hours of the working day.
Result: 11.7 lb of weld metal, 2.5 hr of arc, 8.4 hr elapsed
The same joint over-welded to 3/8
- 1.Going from a 1/4 to a 3/8 leg looks like a 50% increase. It is not.
- 2.Weld metal goes as the square of the leg, so the section goes from 0.03125 to 0.0703 sq in - 125% more.
- 3.100 ft now needs 26.3 lb rather than 11.7, and the arc time goes from 2.5 to 5.6 hours.
- 4.With labour at $85 an hour that is well over a thousand dollars of extra cost, for a weld the drawing did not ask for.
Result: 26.3 lb and 5.6 hr - more than double, for one size up
Stick against MIG on the same job
- 1.The same 11.7 lb of weld metal, but stick deposits about 65% of the electrode - the rest is stub end and slag.
- 2.So 18 lb of electrode has to be bought to deposit 11.7, against 12.3 lb of MIG wire.
- 3.At 3.5 lb/hr gross and 65% efficiency, that is 2.28 lb/hr deposited and over five hours of arc.
- 4.The electrode is cheaper per pound and the job costs far more, because the labour attached to each pound deposited is the largest number in the calculation.
Result: 18 lb of electrode for 11.7 lb of weld, and double the arc time
Why weld size costs so much more than it looks
The section of a fillet weld is a right triangle whose legs are the specified size, so its area is the leg squared over two. That squaring is the whole point: weld metal, and therefore arc time, cost and heat, all scale with the square of the leg size rather than with the leg size itself.
Going from a quarter-inch fillet to a three-eighths looks like a 50% increase and is a 125% one. Going from a quarter to a half looks like doubling and is quadrupling. A welder who habitually runs one size over the drawing is not adding a bit of margin, they are more than doubling the cost of every joint they touch.
And it is invisible. Nobody inspects a weld and complains that it is too large; over-welding passes every check, satisfies every instinct about strength, and quietly consumes a large fraction of a shop's capacity. It also puts far more heat in, which is the other half of the bill - more distortion, more straightening, more time.
Efficiency, and why price per pound misleads
Not all of a consumable becomes weld. Stick electrode leaves a stub in the holder and a layer of slag on the plate, and a two-inch stub off a fourteen-inch rod is fourteen percent gone before the slag is counted - overall deposition efficiency is around 65%. Flux-cored is around 85%, losing its flux as slag. Solid MIG wire is around 95%, and what it loses is spatter.
So buying a hundred pounds of stick electrode gets you sixty-five pounds of weld, and a hundred pounds of MIG wire gets you ninety-five. Before any labour is counted, the cheaper consumable has already lost a third of its price advantage.
Then the labour is counted, and the comparison inverts entirely. Deposition rates differ by more than efficiencies do, and in most fabrication labour and overhead are three to ten times the consumable cost. A process that deposits half again as fast is cheaper per foot of finished weld even if its consumable costs twice as much - which is the argument that moved the industry from stick to wire, and it was never an argument about the price of the metal.
- Solid MIG wire, 95% — Only spatter is lost. The most efficient common consumable.
- Flux-cored, 85% — The flux leaves as slag, and takes a share of the weight with it.
- Submerged arc, 95% — Very high deposition rates as well, which is why it dominates heavy plate.
- Stick, 65% — Stub ends and slag. Cheapest per pound bought and dearest per pound deposited.
- TIG, 98% — Almost nothing wasted, and the slowest deposition of anything.
Operating factor is the bigger lever
Deposition rate describes what happens while the arc is burning. Operating factor describes how much of the day that is, and in manual fabrication it is between 20% and 30% - the rest is tacking, positioning, chipping slag, grinding, changing consumables, moving the work and looking at the drawing.
That means a two-hour welding job occupies most of a working day, and it means the deposition rate is only shaping a fifth of the clock. Doubling the deposition rate on a manual job halves the arc time and cuts the elapsed time by a quarter or less.
Doubling the operating factor cuts elapsed time in half. And it is usually the cheaper thing to change: fixturing so parts do not have to be held, a positioner so welds can be run flat, better fit-up so gaps do not need building up, and staging so the welder is not walking. Shops that measure this find the biggest gains on the floor rather than in the machine, and mechanisation is worth what it is worth largely because it lifts the operating factor above 60% rather than because the arc is faster.
What this assumes, and where it stops
Assumptions
- Weld metal is steel at 0.2836 lb per cubic inch.
- Fillet section is leg squared over two, with 10% added for the convex face that real fillets carry.
- Deposition efficiencies are standard published values by process.
- Deposition rate from wire feed speed is the first-order geometric relationship, which reproduces published settings charts.
Limitations
- Real deposition rate rises slightly faster than this with current, because of resistive heating along the electrode stickout. A long stickout deposits more at the same amperage.
- Groove weld areas have to come from the joint detail. Bevel angle, root opening, root face and any backing all change it, and the difference between joint designs is large.
- It does not count tacking, root passes run with a different process, back-gouging, or repair.
- Operating factor varies enormously by shop, job and position, and the figure entered is doing a great deal of the work in the elapsed time.
- Multi-pass welds on thick sections have interpass temperature requirements that constrain how fast the metal can actually be put down.
Common questions
How much weld metal is in a foot of quarter-inch fillet?
About 0.106 pounds of pure section, or around 0.117 once the convex face real fillets carry is allowed for. The section is the leg squared over two - 0.03125 square inches - and steel is 0.2836 pounds per cubic inch. Every estimating table gives the same figure, and it is worth knowing because everything else scales from it.
Why does one size up cost so much more?
Because weld metal goes as the square of the leg size. A three-eighths fillet is 125% more metal than a quarter, not 50%. A half-inch fillet is four times a quarter. Over-welding by one size on a shop full of joints is a very large and completely invisible cost, and nobody ever rejects a weld for being too big.
Is MIG wire cheaper than stick electrode?
Per pound bought, usually not. Per pound of weld deposited, yes - solid wire puts down about 95% of what you buy and stick about 65%, so a third of every electrode is stub and slag. And once labour is included the comparison is not close, because wire deposits considerably faster and labour is several times the consumable cost in most shops.
What is a realistic operating factor?
Twenty to thirty percent for manual welding in a fabrication shop, once tacking, positioning, chipping, grinding and setup are counted. Semi-automatic work with good fixturing reaches forty to fifty. Mechanised and robotic work runs sixty and above. It is the number that determines how long a job takes, far more than the deposition rate does.
How do I raise deposition rate cheaply?
Go up a wire size if the joint can take the current - the step from 0.035 to 0.045 is 65% more metal at the same feed setting. Beyond that, look at the operating factor rather than the arc: fixturing, positioners so welds run flat, and fit-up good enough that gaps do not need filling. Those usually return more than a faster process would.
Sources
- Welding cost and productivity fundamentals — Lincoln Electric
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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