"Sub ohm" gets thrown around a lot in vape shops and forums, usually next to a cloud thick enough to set off a smoke alarm. This guide is written for people who already vape or smoke and want to understand sub ohm properly before switching styles. It covers what an ohm actually measures, how sub ohm kits differ from mouth-to-lung vaping, and what to know before you buy one.

What is an ohm?

An ohm (symbol Ω) measures how much a coil resists electrical current. Standard replacement coils for mouth-to-lung (MTL) kits, the ones built to feel like a cigarette draw, typically sit between 1.2Ω and 2.0Ω. You'll sometimes see this range called "plus ohm" to distinguish it from what comes next.

A kit counts as sub ohm once the coil resistance drops below 1.0Ω. The Smok TFV12 Prince tank, for example, takes coils from 0.40Ω down to 0.15Ω, and the Aspire Cleito Exo runs a 0.16Ω coil. Lower resistance lets more current reach the coil, so it heats faster and hotter, vaporising more e-liquid and producing the thicker clouds sub ohm vaping is known for.

How do you know if you're using a sub ohm kit?

Coil resistance is printed on the packaging and usually stamped on the coil itself, so that's the fastest way to check. Most modern box mods and pod mods also display resistance on screen the moment you screw a coil in. As a rule of thumb, basic vape pens and simple pod kits are built for MTL and won't fire sub ohm coils at all, while anything sold as an "advanced kit", "box mod" or "sub ohm tank" is designed to.

Sub ohm vs mouth to lung: what's the actual difference?

The clearest way to tell the two styles apart isn't the coil number on the box, it's how you inhale.

MTL vaping pulls vapour into your mouth first, then down into your lungs, the same two-step draw as smoking a cigarette. It uses higher-resistance coils, tighter airflow and lower power, which suits e-liquids with more PG (propylene glycol) and gives a tighter, more discreet vape. It's generally the easier starting point for anyone coming straight off cigarettes.

Sub ohm vaping is direct to lung (DTL): vapour goes straight into your lungs in one motion, more like a deep breath than a drag. It needs wide-open airflow, a lot more power, and high-VG (vegetable glycerine) e-liquid to keep up. That combination is what produces the bigger clouds and stronger flavour sub ohm vapers are after.

Switching from MTL to DTL takes some getting used to, and it's normal to cough on the first few sub ohm draws. It's worth practising the inhale for a bit before you judge the kit.

Why do vapers choose to sub ohm?

Some vapers who've spent time on a standard 1.2Ω to 2.0Ω kit find they want more of a hit than a tighter MTL setup gives them. Because sub ohm coils push through more vapour per puff, most sub ohm vapers run a noticeably lower nicotine strength than they would on an MTL kit: going higher tends to taste harsh rather than more satisfying. Sub ohm setups also tend to carry more adjustable features (wattage, airflow, sometimes temperature control), which lets the experience be tuned rather than fixed.

Regulated mods vs mechanical mods (and why battery safety matters)

Sub ohm devices generally fall into two camps.

Regulated mods have built-in circuitry that limits wattage, checks coil resistance before firing, and cuts power if something's wrong. They're the safer, more forgiving option and the sensible starting point for anyone new to sub ohm vaping.

Mechanical mods have no circuitry at all. Pressing the fire button sends the battery's full output straight to the coil, with nothing to stop a short circuit or a wrongly rated coil. They demand a solid working knowledge of Ohm's law and battery safety; used incorrectly they can genuinely damage a battery or cause it to vent. If you're not confident checking coil resistance with a meter and matching it to what your battery can safely handle, a mechanical mod isn't the place to start.

A few basics that apply to any sub ohm device with removable batteries:

• Use a battery case or holder when carrying spares loose, so they can't short against keys or coins.
• Check batteries are rated for the amp draw your coil needs.
• Never mix old and new batteries in a multi-battery mod.
• Insert batteries the right way round every time.
• Stop using any battery that's damaged, swollen, or unusually hot.

What e-liquid should you use with a sub ohm device?

Sub ohm tanks are built for high-VG e-liquid (typically around 70% VG to 30% PG), because thicker liquid produces bigger clouds and holds up better under the extra heat. You can also run 50/50 e-liquid in a sub ohm device, since it's designed to work across both MTL and sub ohm kits, though you won't get quite the same cloud output as a dedicated high-VG mix.

On nicotine strength, lower is usually better for sub ohm setups: many vapers find 3mg or 6mg the sweet spot, since the bigger, more direct hit from a sub ohm coil gets nicotine into your system faster than a tighter MTL draw.

Are sub ohm kits affected by the UK's vaping rules?

No. The 2025 ban on single-use disposable vapes applies only to devices that are neither rechargeable nor refillable. Sub ohm kits and box mods, with their replaceable coils and refillable tanks, sit outside that ban entirely and remain fully legal to buy and sell.

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