DIY Vape Tools
Ohm's Law calculator for vaping: regulated and mechanical mods
Ohm's law is the maths behind every vape: volts, amps, resistance and watts are all linked, so if you know two you can work out the rest. But how your battery is loaded depends completely on your mod. This calculator does all three jobs: the battery amp draw on a regulated mod (by far the most common today), the direct draw on a mechanical mod, and a full volts, amps, ohms and watts solver. Every result comes with a battery safety check.
Read first. Regulated mods have built-in protection and are the safe, sensible choice for almost everyone. Mechanical (unregulated) mods have no protection at all, so a bad build or a tired battery can be dangerous. Only use a mech mod if you fully understand battery safety. When in doubt, use a regulated mod.
Ohm's Law calculator
Pick your mod type. On a regulated mod you set a wattage; on a mechanical mod the coil and battery decide everything. The solver tab is the classic any-two-values calculator.
On a regulated mod the coil resistance does not change how many amps the battery gives - only the power you set does. As the battery empties its voltage drops, so the current it must give goes up. This uses a 3.2V near-empty cell, the worst case, for the safety check.
On a mechanical (unregulated) mod the battery connects straight to the coil, so amps equal battery volts divided by coil ohms. The draw is highest at a full 4.2V, so that is the figure to check against your battery. There is no board protection, so stay well within the CDR.
Enter any two values and the calculator gives the other two using Ohm's law: V = I × R, and power P = V × I. This is pure electronics, the same maths a mod uses under the hood.
Regulated vs mechanical: why the battery draw is different
This is the part most guides get muddled, so here it is straight.
You set a wattage and the board delivers it, stepping the voltage up or down as needed. The battery drain is watts divided by the battery voltage, the number of cells and the board efficiency. Your coil resistance does not change the battery draw. Protections cut in for shorts, low battery and over-current.
No chip. The battery connects directly to the coil, so the current is simply battery volts divided by coil ohms, at up to 4.2V. A lower resistance pulls more amps. There is no protection, so the build must stay well inside the battery's rating.
Because regulated mods are safer and easier, they are what most people vape on now. Browse regulated mods, high-end mods, and the rebuildables and wire for building on them.
How the maths works
The four quantities relate like this. Voltage equals current times resistance (V = I x R). Power equals voltage times current (P = V x I), which also gives P = V squared divided by R, and P = I squared times R. From any two you can find the other two, which is exactly what the solver tab does.
For battery safety the key figure is amps. On a mechanical mod that is battery volts divided by coil ohms. On a regulated mod it is watts divided by (battery volts x cells x efficiency), and it rises as the battery empties, which is why the calculator uses a near-empty 3.2V cell for the worst case.
Battery safety, the rules that matter
Every cell has a continuous discharge rating (CDR), the highest current in amps it can give safely. Your draw must stay below it, with headroom. Always use the manufacturer's CDR, never the higher pulse figure. Use good, matched cells from a reputable brand, keep spares in a case rather than loose in a pocket, and check builds with an ohm reader before firing. On a regulated mod the board helps; on a mech there is nothing between you and the battery.
If a battery is damaged, stop. A torn wrap, dents or a battery that gets hot in use should be retired safely and recycled, never used. Charge on a good charger, not overnight unattended.
Ohm's Law FAQs
Ohm's law and the power formulas are standard physics. The regulated battery-drain method (watts divided by voltage, cells and efficiency, using a near-empty cell for worst case) and the mechanical direct-draw method follow established vaping battery-safety guidance. This page is general information, not a safety certification; always follow your battery and device manufacturer's instructions.