Vape Coil Wattage Calculator

Calculator

Calculation mode

Measured resistance, ohm

Applied voltage, V

Target coil current, A

Target wattage, W

Wire length per coil, mm

Wire diameter, mm

Coil count

Target heat flux, mW/mm²

Cell count

Minimum cell voltage, V

Battery CDR per cell, A

Device efficiency, %

Device max output voltage, V

Maker minimum watts

Maker maximum watts

Battery safety margin, %

Formula Used

Power from voltage: P = V² / R

Power from current: P = I² × R

Voltage from power: V = √(P × R)

Current from power: I = √(P / R)

Coil surface area: A = π × wire diameter × wire length × coil count

Heat flux: HF = P × 1000 / A

Regulated battery current: Ib = P / (cell count × minimum cell voltage × efficiency)

How to Use This Calculator

Choose the calculation mode that matches your known value.
Enter measured coil resistance in ohms.
Add voltage, current, wattage, or target heat flux.
Enter wire length, wire diameter, and coil count for heat flux.
Add battery rating, cell count, and device efficiency.
Press Calculate to view wattage, current, heat flux, and notices.
Use CSV or PDF buttons to save the report.

Example Data Table

Resistance	Voltage	Wire Length	Wire Diameter	Coils	Wattage	Current	Heat Flux
0.30 ohm	3.70 V	80 mm	0.40 mm	1	45.63 W	12.33 A	453.90 mW/mm²
0.50 ohm	4.20 V	100 mm	0.50 mm	1	35.28 W	8.40 A	224.60 mW/mm²
0.80 ohm	5.00 V	120 mm	0.32 mm	1	31.25 W	6.25 A	259.05 mW/mm²

Advanced Coil Wattage Planning

Coil wattage depends on resistance, applied voltage, current, and coil surface area. A small change in resistance can change power quickly. This calculator uses common electrical relationships to estimate output and battery demand. It also estimates heat flux from wire length and diameter. Heat flux helps describe how hard each square millimeter of coil is driven.

Why Wattage Matters

Too little power can make a coil slow and weak. Too much power can overheat wire, cotton, or liquid. It can also stress batteries and device electronics. A regulated device adds another limit because it draws current from cells through a converter. The converter is not perfect, so efficiency matters. This page includes that loss in the battery current estimate.

Using Heat Flux

Heat flux is shown in milliwatts per square millimeter. Lower values usually feel cooler. Higher values usually feel warmer. The ranges shown here are only planning labels. They are not a guarantee of safety or comfort. Coil material, airflow, wick saturation, and liquid choice also change the result. Always compare the answer with the coil maker wattage range.

Battery Awareness

Battery current should stay below the continuous discharge rating. Extra headroom is important. Old cells, damaged wraps, heat, and poor contacts can reduce safety. Mechanical devices require more care because the coil is connected directly to the cell circuit. Regulated devices can still overload cells when wattage is high and cell voltage is low.

Practical Build Notes

Enter measured resistance from a trusted meter. Do not rely only on a printed value. Use the lowest expected resistance for safety checks. If the result is high, reduce voltage or wattage. You can also increase resistance or coil surface area. For dual coils, enter the combined resistance if your device reads total resistance. Use the coil count field only for heat flux area.

Best Use

This calculator is best for comparing setups before use. It supports Ohm law, target wattage, current, and heat flux modes. Export the report for records. The final decision should follow device limits, battery limits, and coil manufacturer guidance.

Record each change after testing. Good notes make repeated builds easier. They also help spot unusual resistance shifts before problems grow again later.

FAQs

What does this calculator estimate?

It estimates coil wattage, voltage, current, heat flux, battery current, and margin. It uses Ohm law and entered battery data. The result is a planning guide, not a safety certificate.

Which resistance value should I enter?

Enter the measured resistance shown by a trusted meter or device. Use the lowest expected value when checking limits. Small resistance changes can raise current quickly.

What is heat flux?

Heat flux is wattage spread across coil surface area. It is shown in milliwatts per square millimeter. Higher heat flux usually means a warmer and more aggressive coil.

Does this work for dual coils?

Yes. Enter the total resistance read by the device. Then enter the coil count for heat flux area. The calculator uses coil count only for surface area estimation.

What battery value is used?

The tool uses continuous discharge rating, cell count, minimum cell voltage, and efficiency. It estimates current demand per cell for regulated power planning.

Why include device efficiency?

A regulated device loses some energy during conversion. Efficiency helps estimate real battery demand. Lower efficiency raises the current drawn from each cell.

Can I export my result?

Yes. Use the CSV button for spreadsheet data. Use the PDF button for a simple printable report. Both include main results and notices.

Is the result a safety guarantee?

No. The result depends on entered values and assumptions. Always follow device limits, battery ratings, coil maker ranges, and proper electrical safety checks.