How much power do 300-ohm headphones need?

Impedance alone is not enough. For a hypothetical 300-ohm headphone rated at 102 dB SPL per milliwatt, a 110 dB SPL target requires about 6.31 mW and 1.38 V RMS at the headphone load. A different sensitivity changes both results.

Can I enter sensitivity quoted per volt?

This calculator accepts dB SPL per milliwatt. Convert a per-volt figure first: S_mW = S_V - 10 log10(1000 / R), where R is headphone impedance in ohms. At 300 ohms, subtract about 5.23 dB from the per-volt sensitivity.

What does the damping factor tell me?

It is headphone impedance divided by amplifier output impedance. A ratio of at least 8:1 is a common rule of thumb for limiting interaction with the headphone's impedance curve. It is not a sound-quality rating or a guarantee of a flat response.

Is 110 dB SPL a recommended listening level?

No. It is an example peak target for comparing amplifier capability, not a recommended listening level. The calculator does not measure sound at your ears or determine a safe listening duration.

Headphone Power Sizer

Headphone DAC & Amp Power Calculator

Enter headphone impedance, sensitivity in dB SPL per milliwatt and a target peak level. This headphone power calculator estimates amplifier output in mW, RMS voltage and the damping ratio. Calculations run in your browser, with no signup.

Headphone Impedance (Ohms Ω)

Sensitivity (dB SPL / mW)

If your specification is per volt, use the conversion below first.

Target Peak SPL (dBSPL)

Amp Output Impedance (Ohms Ω)

Peak targets are calculation inputs, not listening recommendations.

Required Amp Power

6.31 mW

Required RMS Voltage

1.38 Vrms

Damping Factor

3000:1 (At least 8:1)

How much power do my headphones need?

Start with the manufacturer's impedance and sensitivity figures. As JDS Labs explains, sensitivity and the desired sound pressure level determine the power requirement; impedance then connects that power to voltage. An impedance number alone cannot tell you whether a headphone is difficult to drive.

For sensitivity S in dB SPL per milliwatt and target level L in dB SPL, P_mW = 10^((L - S) / 10). With headphone impedance R in ohms, V_RMS = sqrt(P_mW × R / 1000), from the electrical relation P = V² / R. This is a nominal-load estimate using published sensitivity, not a measurement of your headphones or a prediction of their response at every frequency.

Worked example: 300 Ω, 102 dB/mW, 110 dBSPL

These are hypothetical specifications, not a claim about a particular model. The target is 8 dB above the 1 mW sensitivity reference: 10^(8 / 10) = 6.31 mW. Converting that to watts and applying the 300-ohm load gives sqrt(0.00631 × 300) = 1.38 V RMS. With an amplifier output impedance of 0.1 ohm, the damping ratio is 300 / 0.1 = 3000:1.

Compare the result with the amplifier's output rating into 300 ohms, including the stated distortion limit. A rating into 32 ohms is not the same operating condition. The calculator estimates voltage at the headphone load; it does not add allowance for an amplifier's internal voltage drop or establish its current and clipping limits.

What the mW, RMS and damping outputs mean

mW: estimated electrical power per channel needed at the selected acoustic target. It is a requirement to compare with a rated output, not a recommendation to listen at maximum volume.
RMS voltage: the effective voltage across the headphone load corresponding to that power. It is not the amplifier's supply voltage or peak-to-peak voltage.
Damping ratio: headphone impedance divided by amplifier output impedance. The 8:1 rule of thumb corresponds to about 1 dB of voltage-divider loss at the impedance used. Nominal impedance alone cannot guarantee the response across frequency.
A larger damping number is not a quality score. Benchmark's output-impedance note explains the electrical interaction; noise, distortion and available output still need separate checks. Zero output impedance gives an idealized infinite ratio.

Guides that use this result

Matching a DAC and headphone amp to your headphones
Where impedance, sensitivity and output impedance come from, and what SINAD does not tell you.
Do you need a DAC and amp?
Turning the number above into a buy or skip decision.
Combo DAC/amp vs separates
One box or two, once you know the output you need.
Headphone amp hiss and hum: causes and fixes
When the problem is noise rather than a shortage of drive.

Converting sensitivity from dB/V to dB/mW

A per-volt figure uses a different reference power. At 1 V RMS, power in milliwatts is 1000 / R. Subtract 10 log10(1000 / R) from the per-volt sensitivity before entering it here. For 300 ohms, that subtraction is about 5.23 dB. Entering the unconverted number would underestimate the power needed in this example.

The headphone matching guide connects these numbers to output ratings and gain. If the issue is hiss or hum, use the noise guide above: a larger power rating does not diagnose the cause.

Frequently asked questions

How much power do 300-ohm headphones need?: Impedance alone is not enough. For a hypothetical 300-ohm headphone rated at 102 dB SPL per milliwatt, a 110 dB SPL target requires about 6.31 mW and 1.38 V RMS at the headphone load. A different sensitivity changes both results.
Can I enter sensitivity quoted per volt?: This calculator accepts dB SPL per milliwatt. Convert a per-volt figure first: S_mW = S_V - 10 log10(1000 / R), where R is headphone impedance in ohms. At 300 ohms, subtract about 5.23 dB from the per-volt sensitivity.
What does the damping factor tell me?: It is headphone impedance divided by amplifier output impedance. A ratio of at least 8:1 is a common rule of thumb for limiting interaction with the headphone's impedance curve. It is not a sound-quality rating or a guarantee of a flat response.
Is 110 dB SPL a recommended listening level?: No. It is an example peak target for comparing amplifier capability, not a recommended listening level. The calculator does not measure sound at your ears or determine a safe listening duration.