Kanthal A1 wire, AWG gauge, diameter and ohms per metre

The spool says kanthal A1 26 AWG, the calculator wants a diameter in millimetres, and the ohm reader shows a figure that doesn’t quite match your plan. The American gauge, the rounding on labels and the resistivity of the alloy are three measuring systems meeting on the same coil. Until they line up, every build involves a bit of guesswork, and switching wire means starting again from scratch.

Kanthal A1 in three numbers that matter at the bench

Kanthal A1 is a resistance wire made from an iron-chromium-aluminium alloy. Our alloy data come from the material datasheets that the manufacturer Kanthal, part of the Alleima group, publishes for Kanthal A-1 and Nikrothal 80. The A-1 sheet gives a resistivity of 1.45 Ω·mm²/m at 20 °C.

Three numbers are then enough to work with. The first is that resistivity, the second the real wire diameter in millimetres, the third the wrapped length. A coil’s resistance follows directly, resistivity times length divided by cross-section.

In practice, 0.40 mm wire, sold as 26 AWG, has 11.54 Ω per metre. Six wraps on a 3 mm rod give a coil of about 0.74 Ω, legs aside. And since its resistance barely moves as it heats, this wire is vaped in power mode, never in temperature control.

Reading an AWG gauge without picking the wrong wire

AWG, short for American Wire Gauge, numbers wire backwards. The higher the figure, the thinner the wire, on a fixed geometric scale rather than a list of round numbers, which explains a good many label discrepancies.

The AWG table in millimetres

The ASTM B258 standard sets gauge 36 at 0.127 mm and a constant ratio from one gauge to the next, the 39th root of 92, about 1.1229. The table covers the gauges that matter for rebuilding, with the resistance per metre we work out for kanthal A1.

AWG gauge	Theoretical diameter	Kanthal A1, resistance per metre
22	0.644 mm	4.45 Ω
24	0.511 mm	7.08 Ω
26	0.405 mm	11.26 Ω
28	0.321 mm	17.91 Ω
30	0.255 mm	28.47 Ω
32	0.202 mm	45.27 Ω

Moving two gauges multiplies the resistance per metre by 1.59, so a 28 AWG coil is about 60% more resistive than its 26 AWG twin.

When the label rounds the diameter

Spools rarely say 0.405 mm. Among the retailers we checked, 26 AWG is labelled 0.40 mm and 24 AWG 0.50 mm. Finer wire is where labels part company. One shop sells 0.30 mm as 28 AWG, another files it under 29, a third sells its 28 AWG as 0.32 mm.

The difference matters. At 0.30 mm, kanthal A1 reads 20.51 Ω/m, against 18.03 Ω/m at 0.32 mm, almost 14% more for wire supposedly carrying the same number. For 26 AWG, rounding to 0.40 mm weighs less, around 2.5% extra resistance.

At the workshop, the millimetre figure printed on the spool is what goes into the sum, never the gauge number. All our calculations start from 0.40 mm at 11.54 Ω per metre.

What kanthal diameter does to your ohms

A wrap is measured along the centre line of the wire, so on a diameter equal to the rod plus the wire. On a 3 mm rod, 0.40 mm wire traces a mean circle of 3.40 mm, which is 10.68 mm of wire per turn. Changing the diameter barely alters that length, but it transforms the cross-section.

Wire, 6 wraps on a 3 mm rod	Wrapped length	Resistance
0.32 mm	62.58 mm	1.13 Ω
0.40 mm	64.09 mm	0.74 Ω
0.50 mm	65.97 mm	0.49 Ω

The 0.50 mm wire makes the coil only 5% longer than the 0.32 mm one, yet cuts its resistance by a factor of 2.3. The cross-section, which scales with the square of the diameter, calls the tune.

Keep the weight of a single wrap in mind too. On our 0.40 mm reference build, each turn added or removed shifts the resistance by 0.12 Ω. The full working, legs included, is laid out in our coil calculator checked by hand.

The builds where kanthal feels at home

High resistivity and a resistance that stays put under heat make kanthal a versatile working wire. It still has its favourite ground, and one area where it becomes less convenient.

Single coils in power mode

This is its natural use. The workshop’s reference coil, six wraps of 0.40 mm on 3 mm, lands around 0.74 Ω and is set in watts on a regulated mod. Because the cold reading matches the hot wire, the power you dial in is what the coil actually receives.

Higher-resistance builds for a tight draw

Above 1 Ω, kanthal saves space. In 0.32 mm, seven wraps on a 2.5 mm rod use 62.0 mm of wire for 1.12 Ω. With nichrome 80, whose resistivity drops to 1.09 Ω·mm²/m, the same value would need 82.5 mm of wire, a coil a third longer and harder to fit on a small deck.

Where it gets less convenient

Very low-ohm builds call for thick wire, and thick kanthal is harder work. The bending stiffness of a wire rises with the fourth power of its diameter, so going from 0.40 to 0.50 mm makes it 2.4 times stiffer to wrap. In 0.50 mm, two six-wrap coils in parallel drop to 0.24 Ω, territory where you need to know the limits of your mod and batteries precisely.

Why kanthal has no place in temperature control

A mod’s temperature control doesn’t measure heat directly. It tracks the rise in coil resistance during a draw and infers the temperature from it, which calls for a wire whose resistance climbs clearly and predictably.

Kanthal A1 does the exact opposite. Its temperature factor of resistivity stays at 1.00 from 100 to 400 °C and only reaches 1.05 at 1,400 °C. Our 0.74 Ω coil therefore still reads 0.74 Ω at 400 °C, leaving the mod nothing to work with.

A kanthal build is set in power mode as a result. The Ni, Ti and SS modes stand for nickel, titanium and stainless steel, the alloys that Vaping360 lists among the wires designed for that setting. If your mod offers them, leave them alone for this wire.

Checking a kanthal spool before you build

An unlabelled spool can be sorted with a simple magnet. Kanthal A-1 is magnetic at room temperature, whereas Nikrothal 80, the same maker’s nichrome, is not. If the magnet pulls the wire, it isn’t nichrome, although some ferritic stainless steels react too, which is why the label is worth keeping.

Once built, the coil is checked with an ohm reader before the first draw. On our reference build, the reading should land near 0.74 Ω, slightly above depending on how much leg sits between the coil and the screws. A clearly lower value points to a wrap touching the deck, an unstable one to a loose screw. Strip it down and start again until you get a stable value within the range your mod and batteries accept.

FAQ

Five questions that come up at the bench, and that the sections above leave aside.

How many wraps for 26 gauge kanthal A1?

It depends on the target resistance and the rod. On a 3 mm rod in 0.40 mm, five wraps give about 0.62 Ω, six wraps 0.74 Ω and eight wraps 0.99 Ω, legs aside.

And how many wraps with 24 gauge kanthal A1?

Sold as 0.50 mm, 24 AWG adds only 0.08 Ω per wrap on a 3 mm rod. Five wraps give 0.41 Ω, six give 0.49 Ω and eight give 0.65 Ω.

Does kanthal stay magnetic when it heats up?

No. Kanthal A-1 stops being magnetic at around 600 °C, its Curie point. The magnet test is therefore done on a cold spool, never on a coil fresh from a dry fire.

Should you enter the gauge or the diameter in a calculator?

The diameter in millimetres, every time. Brands don’t round gauges the same way, and it is the real cross-section of the wire that sets the resistance. The coil wire meter on the workshop’s home page works in millimetres for the same reason.

Does thinner kanthal heat up faster?

Yes, at the same power. Using the alloy’s density of 7.10 g/cm³, six wraps of 0.32 mm on 3 mm weigh 36 mg, against 57 mg in 0.40 mm and 92 mg in 0.50 mm. Less mass needs less energy to reach the same temperature.

Choose your kanthal by the millimetre, not the number

Kanthal A1 remains one of the easiest wires to calculate, because its value hardly changes as it heats. You still need the right diameter to start from. Note the millimetre figure on the spool, work out the cross-section, count your wraps along the centre line of the wire, and the ohm reader will confirm what the paper predicted.

The workshop applies this method to every resistance wire, and kanthal remains the best place to practise it before moving on to twisted and fused wires.

Also on the bench

Build notes from L’Atelier Brouillard, for adult readers only. Vaping products usually contain nicotine, which is addictive, and nicotine vaping products are not for sale to under-18s in the UK. Nothing here is a recommendation to buy.