Headphone Power Calculator (mW & volts needed from sensitivity and impedance)

Understanding the headphone power calculator — concept and principle

Will your phone or amplifier drive a pair of headphones loud enough? This calculator uses the headphones' sensitivity and impedance to work out the power, voltage and current needed for a chosen listening level, and converts sensitivity between dB per milliwatt and dB per volt.

8 dB above the 1 mW rating needs 6.31 mW, or 0.449 V into 32 Ω.

How it is calculated

Power needed P = 1 mW × 10^((L − S_mW) ÷ 10)

Voltage V = √(P × Z); current I = V ÷ Z

Converting sensitivity: S_V = S_mW + 10 log₁₀(1,000 ÷ Z)

Power for 3 dB more = P × 10^0.3 (about double)

L is the target level in dB SPL, S_mW the sensitivity in dB SPL for 1 mW, Z the impedance in ohms.

The principle

Sensitivity tells you how loud the headphones play with a reference input. Decibels are logarithmic: every 10 dB louder needs ten times the power, and every 3 dB needs about twice the power. So the power needed rises steeply with level. Ohm's law then converts power into the voltage and current the amplifier must supply. High-impedance headphones need more voltage, low-impedance ones more current, and the amplifier must provide both at once without distortion.

Worked example

Default inputs: sensitivity 102 dB SPL/mW, impedance 32 Ω, target 110 dB SPL.

Level above the reference = 110 − 102 = 8 dB.
Power = 10^(8 ÷ 10) = 6.31 mW.
Voltage = √(0.00631 × 32) = 0.449 V RMS.
Current = 0.449 ÷ 32 = 14 mA RMS.
Sensitivity per volt = 102 + 10 log₁₀(1,000 ÷ 32) = 116.9 dB/V; 3 dB more needs 12.59 mW.

Each point is the calculator re-run with only “Loudest level you want (dB SPL)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Loudest level you want (dB SPL)	Power needed (mW)
27.5	0
55	0
82.5	0.01
110	6.31
138	3,548.13
165	1,995,262.31
220	630,957,344,480.19

How to read the result

Compare the voltage and power with your source's specifications. Many headphones need only a few milliwatts for loud listening, but low-sensitivity or high-impedance models may need a dedicated amplifier. Leave headroom for musical peaks, which are louder than the average level. Note that 110 dB SPL is very loud: prolonged listening at high levels can damage hearing, so the target here is a maximum, not a recommended listening level.

Common mistakes

Mixing up dB/mW and dB/V sensitivity specifications.
Ignoring that impedance varies with frequency.
Choosing a target level that is unsafe for regular listening.
Assuming a powerful amplifier is always needed; voltage, not just power, matters.

Keep in mind: High sound levels can cause permanent hearing damage. Keep listening levels and durations moderate; this calculation is not a safety guideline.

Frequently asked questions

What does dB/mW mean?

The sound level the headphones produce with 1 milliwatt of input.

How do I convert dB/V to dB/mW?

Subtract 10 log₁₀(1,000 ÷ Z) from the dB/V figure.

Why does 3 dB more need double the power?

10 log₁₀(2) ≈ 3, so doubling power adds about 3 dB.

Do high-impedance headphones need an amplifier?

Often, because they need more voltage than many phones can provide.

Sources: ITU-R Recommendation V.574-5, "Use of the decibel and the neper in telecommunications" · D. Bohn, RaneNote 100, "Headphone Power" (Rane Corporation)

Checked 9 Nov 2026. ITU-R Recommendation V.574-5 (08/2015), “Use of the decibel and the neper in telecommunications”, Annex 1 §1.2 and §6.1 (power ratio 10 lg, dBm relative to 1 mW); D. Bohn, RaneNote 100 “Headphone Power” (Rane Corporation): sensitivity as dB SPL produced by 1 mW input; Ohm’s law P = V²/R.

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