What Are Ohms and Sub-Ohm Vaping? | Vape School
Ohms, volts, amps and watts can make vaping sound like an electrical engineering class. You do not need a degree to understand them, though, and knowing the basics helps you pick the right coil, get the vapor and flavor you want, and keep your battery within its limits.
This guide explains each term in plain English, shows how they work together, and covers what sub-ohm vaping is and who it suits.
Short version: Ohms measure your coil’s resistance. Sub-ohm means a coil below 1.0 ohm, which runs at higher power for bigger clouds and warmer vapor. Lower resistance and higher power both draw more current from your battery, so always know your battery’s continuous discharge rating.
The four terms you need to know
Volts (V)
Voltage is electrical pressure, the force that pushes current through your coil. A lithium-ion vaping battery reads about 4.2 volts when fully charged, has a nominal voltage of about 3.6 to 3.7 volts, and drops as it drains. On a regulated mod, the circuit board controls the voltage that reaches your coil. On a mechanical mod, your coil gets whatever the battery has left.
Ohms (Ω)
Ohms measure resistance: how strongly your coil resists the flow of current. Three things set a coil’s resistance: the wire material, the wire’s thickness and its length. Thicker wire lowers resistance, and so does shorter wire. Coils made with several strands side by side, or atomizers with two coils, also come out lower.
Prebuilt coils have their resistance printed on them. If you build your own, an ohm reader tells you exactly where you landed. Our vape tool kit guide covers what to get.
Amps (A)
Amps measure current, the amount of electricity flowing through the circuit. The lower your coil’s resistance, or the higher the power you set, the more current your battery has to supply. Every battery has a continuous discharge rating (CDR): the most current it can deliver steadily without being pushed past its limits.
Watts (W)
Watts measure power, and power is what heats your coil. More watts means a hotter coil, more vapor and warmer vapor, up to the point where the wick cannot keep up and you get a dry hit. Most regulated mods let you set the wattage directly, and most coils list a recommended wattage range.
How they fit together
Ohm’s law, plus a simple formula for power, ties the four terms together:
- Amps = volts ÷ ohms
- Volts = amps × ohms
- Watts = volts × amps
Take a fully charged battery at 4.2 volts and a 0.5 ohm coil. The current is 4.2 ÷ 0.5 = 8.4 amps, and the power is 4.2 × 8.4, about 35 watts. Drop to a 0.25 ohm coil at the same voltage and the current doubles to 16.8 amps, for about 71 watts.
That math applies directly to mechanical mods, where nothing limits the current. On a regulated mod, the battery’s current depends mostly on the wattage you set: roughly watts divided by battery voltage, plus a little extra for the circuit’s losses, and more as the battery drains. At 40 watts, a single battery at 3.6 volts supplies at least 11 amps.
Either way, keep your current draw comfortably below your battery’s CDR. Our list of recommended batteries for vaping covers the ratings to look for.
What sub-ohm vaping means
Sub-ohm vaping simply means using a coil with a resistance below 1.0 ohm. Low-resistance coils are built to run at higher wattages and heat more e-liquid at once. The result is bigger clouds, warmer vapor and, for many vapers, fuller flavor, which is why sub-ohm tanks became the go-to setup for cloud chasers.
Coils at 1.0 ohm and above run at lower power. They make less vapor, and cooler vapor, and they are usually paired with a tighter, mouth-to-lung draw.
| Typical setup | Sub-ohm (below 1.0 ohm) | 1.0 ohm and above |
|---|---|---|
| Draw | Direct-to-lung, airy | Mouth-to-lung, tighter |
| Power | Higher wattage | Lower wattage |
| Vapor | Bigger, warmer clouds | Smaller, cooler vapor |
| E-liquid | Higher VG, lower nicotine | Often higher nicotine, including nic salts |
| Liquid use | High | Low |
Is sub-ohm vaping right for you?
Sub-ohm vaping suits you if you want big clouds and a loose, direct-to-lung draw, and you do not mind refilling often. Keep these points in mind:
- Use lower nicotine. Sub-ohm devices vaporize a lot of liquid, so they pair with lower nicotine strengths. High-strength nic salts are made for low-power pod systems, not sub-ohm tanks. See our guides to nicotine strength and nic salts.
- Pick higher-VG vape juice. VG-heavy e-liquid makes denser clouds and suits the larger wicking ports on sub-ohm coils. Read what PG and VG are. If you go through a lot of juice, the Zamplebox Club‘s Big Juice Box ships four bottles of 100 ml or more a month for $49.99.
- Stay within the coil’s wattage range. Start at the low end and work up. Too much power scorches the wick.
- Respect your battery. Sub-ohm setups ask a lot of batteries. Use authentic, undamaged cells with an adequate CDR, and if you use a mechanical mod, read our single-battery mech safety guide first.
For a closer look at sub-ohm tanks, drippers and rebuildable tanks, read the three types of sub-ohm atomizers.
Common questions
What does sub-ohm mean?
It means a coil resistance below 1.0 ohm. Sub-ohm coils run at higher wattages and produce more vapor.
Does a lower-ohm coil hit harder?
On a mechanical mod, yes: at the same voltage, lower resistance draws more current and makes more power. On a regulated mod, the wattage you set decides the power, and the coil’s resistance mainly decides which wattage range works well.
Can I use nic salts in a sub-ohm tank?
High-strength nic salts are a poor match for sub-ohm tanks, because the tank vaporizes a lot of liquid at once. Use freebase vape juice at a lower strength instead.
Can a low-resistance coil hurt my battery?
Any setup that draws more current than the battery’s continuous rating pushes it past its limits, which can make it overheat. Check your battery’s CDR and do the math before you vape.
WARNING: This product contains nicotine. Nicotine is an addictive chemical. For adults 21+ only.