Headphone Power Calculator — Required Amplifier Output
Enter your headphone sensitivity and impedance plus your target listening level and source output voltage to find out exactly how much power is needed — and whether your source can deliver it.
dB/mW
Ω
dB SPL
mV
Source may be underpowered for the target level.
- 1
SPL gap (target − sensitivity)
110 − 100 = 10 - 2
Power exponent
10 ÷ 10 = 1 - 3
Required power
10^(10 ÷ 10) = 10Milliwatts needed to drive the headphone to the target SPL.
How does this calculator work?
Required power (mW) = 10^((target dB SPL − sensitivity dB/mW) / 10). Required voltage (V) = √(P_mW × impedance / 1000). A 100 dB/mW, 32 Ω headphone needs 10 mW and 0.57 V rms to produce 110 dB SPL — far more than a smartphone's typical 150 mV output. High-impedance cans need dedicated amplifiers.
Formula
How this is calculated
Headphone sensitivity (dB SPL / mW) tells you how loud a headphone gets for one milliwatt of input power. To reach a target sound pressure level (SPL), you invert the relationship: required power P = 10^((target SPL − sensitivity) / 10) mW. For example, a 100 dB/mW headphone needs 10^((110 − 100)/10) = 10 mW to produce 110 dB SPL. High-sensitivity in-ears (e.g. 115 dB/mW) need only 0.03 mW for the same output, while low-sensitivity 250 Ω studio cans (95 dB/mW) need over 300 mW — explaining why they need a dedicated amplifier.
The required driving voltage follows from Ohm's law applied to power: P = V²/R, so V = √(P × R). A 32 Ω headphone needing 10 mW requires √(0.01 × 32) ≈ 0.566 V rms. Most smartphone headphone outputs deliver 100–200 mV rms — enough for sensitive, low-impedance IEMs but not for power-hungry planar magnetic or high-impedance headphones.
The "achievable SPL" inverts the formula using your source's actual output voltage to compute the power it can deliver into the headphone impedance, then converts back to SPL. Headroom (dB above target) indicates how much dynamic range your source has: at least 10–15 dB is recommended so transient peaks are not clipped. Values are based on a purely resistive headphone model — real headphones have reactive impedance peaks, particularly dynamic drivers with voice coils, which can affect measured voltage and SPL.
Frequently asked questions
This calculator uses dB/mW, the most common specification. If your headphone's spec sheet lists sensitivity as dB/V, convert it: dB/mW = dB/V − 10 × log10(impedance). For example, a 110 dB/V headphone at 32 Ω gives 110 − 15 = 95 dB/mW.
At the same voltage, higher impedance draws less current and therefore less power (P = V²/R). So a high-impedance headphone needs a higher output voltage to get the same power — and thus the same SPL — compared to a low-impedance one. This is why studio headphones require dedicated amplifiers while portable in-ears can run from a phone.
OSHA guidelines suggest 90 dB SPL for no more than 8 hours; 100 dB for 2 hours; 110 dB for about 30 minutes. The EU Electronics Directive limits portable music devices to 85 dB averaged output. In practice, most casual listening occurs at 70–85 dB — the 110 dB target in the default is for headroom checking, not sustained use.
Also known as
TG we-Calculate Editorial Team. (2026). Headphone Power Calculator — Required Amplifier Output [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/headphone-power-calculator
TG we-Calculate Editorial Team. "Headphone Power Calculator — Required Amplifier Output." TG we-Calculate. 2026. https://we-calculate.com/calculator/headphone-power-calculator.
TG we-Calculate Editorial Team, "Headphone Power Calculator — Required Amplifier Output," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/headphone-power-calculator
@misc{wecalculate_headphone_power_calculator, title = {Headphone Power Calculator — Required Amplifier Output}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/headphone-power-calculator}}, year = {2026}, note = {TG we-Calculate} }
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