Electrode consumption: pieces and kilos per metre of weld
How many kilograms of electrodes a job needs — and therefore how many packets to order. The calculation goes through the deposited metal, which is the only honest way to do it.
Short answer
A kilogram holds roughly 44 × 2.5 mm, 27 × 3.2 mm, 13 × 4.0 mm. The calculator below turns that into metres of weld: kilograms, pieces and whole packets.
How it is worked out
First the cross-sectional area of the weld: for a fillet it is
z² / 2 plus about 10 % for convexity; for a V butt it comes
from the included angle, the thickness, the root gap and the root face.
Multiplying by the length and by the density of steel, 7.85 g/cm³, gives the
mass of deposited metal.
The mass of electrodes is larger than that, because the stub, the coating and the spatter never reach the joint. The loss factor covers this: 1.5 for careful shop work, 1.6 typically, 1.7 on site and overhead, 1.8 where conditions are bad enough that you would rather not know.
Ordering by the result
Round up to whole packets and add one. Electrodes that stay dry keep; a job stopped at four in the afternoon because a packet ran out costs more than the packet. If the material is a basic type, remember that an opened packet needs re-baking after a shift in humid air — see electrode coating types.
The loss factor
| Factor | When to take it |
|---|---|
| 1.5 | Shop floor, flat position, careful work, short stubs |
| 1.6 | Ordinary conditions — the default |
| 1.7 | Site work, overhead and vertical welds |
| 1.8 | Work at height, cramped space, many tacks |
Mass of one electrode
| Diameter × length | Mass, g | Pieces in 5 kg |
|---|---|---|
| 2.0 × 300 | 13 | 398 |
| 2.5 × 350 | 23 | 218 |
| 3.0 × 350 | 33 | 151 |
| 3.2 × 350 | 38 | 133 |
| 4.0 × 450 | 75 | 66 |
| 5.0 × 450 | 118 | 42 |
Core plus coating: core volume times the density of steel times 1.7. The same arithmetic the calculator above runs, so the two cannot drift apart.
Frequently asked questions
Why is the loss factor so large?
Because only part of a stick electrode ends up in the weld. The stub in the holder, the coating, the spatter and the grinding together take 35 to 45 %. That is why the calculator works with a factor of 1.5 to 1.8 and not 1.0.
How many electrodes are there in a kilogram?
It depends on the diameter: about 55 per kilogram at 2.5 mm × 350 mm, about 33 at 3.2 mm × 350 mm, about 15 at 4 mm × 450 mm. The calculator uses the diameter and length you choose.
Do I count the tack welds separately?
Not normally — they disappear into the loss factor as long as they are ordinary tacks. If a part is tacked heavily because it would otherwise pull, enter the tack length as a weld of its own.
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