Headphone Power Calculator
How many milliwatts, volts and milliamps do your headphones need to hit a target loudness — and can your source actually deliver it?
1 · Your headphones
Source: Audio-Technica spec sheet (sensitivity reference not stated; read as dB/mW @ 1 kHz).
2 · Target loudness
Music peaks sit 15–20 dB above the average level. Sizing for 110 dB peaks ≈ comfortable ~90 dB average listening with headroom to spare.
3 · Power required
Sensitivity equivalents: –
4 · Can your source drive it?
Source figures are typical values — real devices vary. Check your device's spec sheet for its actual maximum output voltage.
Methodology
Given sensitivity S (dB/mW), impedance R (Ω) and target SPL T (dB):
Vrms = √(PW × R) · I = Vrms / R · Vpeak = Vrms × √2
Converting between the two sensitivity standards (1 Vrms into R Ω delivers 1000/R mW):
Worked example — ATH-M50x (99 dB/mW, 38 Ω) at 110 dB: P = 10((110−99)/10) = 12.59 mW; Vrms = √(0.01259 × 38) = 0.692 V; Vpeak = 0.978 V; I = 18.2 mA. Equivalent sensitivity: 113.20 dB/V.
Worked example — Sennheiser HD 600 (97 dB/V, 300 Ω) at 110 dB: 97 dB/V = 91.77 dB/mW; P = 66.51 mW; Vrms = 4.467 V; Vpeak = 6.317 V; I = 14.9 mA. A 1 Vrms dongle manages only 97.00 dB SPL — 13.00 dB short of 110 dB peaks.
Formula basis: decibel power-ratio definition L = 10·log10(P/P0) (sengpielaudio.com dB reference; ece.uvic.ca dB tables) with P0 = 1 mW, plus Ohm's law P = V²/R. Preset specs: Sennheiser (HD 600 / HD 650 SPL at 1 V), Audio-Technica (ATH-M50x), beyerdynamic (DT 770 Pro nominal SPL @ 1 mW), HIFIMAN (Sundara) manufacturer datasheets.
Frequently asked questions
How much power do my headphones actually need?
It depends on three numbers: your headphone's sensitivity, its impedance, and how loud you want peaks to reach. The formula is P(mW) = 10^((target SPL - sensitivity in dB/mW)/10). Example: the Audio-Technica ATH-M50x (99 dB/mW, 38 ohms) needs 12.59 mW to hit 110 dB peaks, which is 0.692 Vrms, 0.978 V peak, and 18.2 mA of current.
What is the difference between dB/mW and dB/V sensitivity?
They are two standards for the same idea. dB/mW is the SPL produced by 1 milliwatt of input power; dB/V is the SPL produced by 1 Vrms of input voltage (both at 1 kHz). Convert with: dB/V = dB/mW + 10 x log10(1000 / impedance in ohms). Example: the ATH-M50x at 99 dB/mW and 38 ohms equals 113.20 dB/V. Mixing the standards up is the most common mistake in headphone power math.
How many volts does the Sennheiser HD 600 need?
The HD 600 is rated 97 dB/V at 300 ohms, which equals 91.77 dB/mW. For 110 dB peaks it needs 66.51 mW, or 4.467 Vrms (6.317 V peak) at 14.9 mA. That is why it sounds quiet straight out of a phone: most phones and dongles cannot deliver 4.5 Vrms.
Can a 1 Vrms phone dongle drive the Sennheiser HD 600?
Not to full dynamic peaks. A 1 Vrms source into 300 ohms delivers 3.33 mW, which drives the HD 600 to a maximum of 97.00 dB SPL - that is 13.00 dB short of 110 dB peaks. It will still play music, but loud passages will clip or sound compressed. A desktop amp (~5 Vrms) reaches 110.98 dB, just enough.
What target SPL should I enter?
Use 110 dB if you want realistic dynamic headroom - music peaks routinely sit 15-20 dB above the average level, so 110 dB peaks correspond to a comfortable ~90 dB average. Use 85 dB to check power for safe long-session average listening (NIOSH recommends no more than 85 dBA over 8 hours). 115 dB is for extreme classical/orchestral peaks.
What is V peak, and why does the calculator show it?
V peak is the highest instantaneous voltage of the waveform: V peak = Vrms x sqrt(2), about 1.414 x Vrms for a sine wave. Amplifiers clip when the signal's peak exceeds their supply rails, so V peak tells you whether the amp itself - not just its average power - can pass the transient cleanly.
Does high impedance alone mean headphones are hard to drive?
No - sensitivity matters more. Compare: the 300-ohm Sennheiser HD 650 (103 dB/V) needs only 16.71 mW for 110 dB peaks, while the 80-ohm Beyerdynamic DT 770 Pro (96 dB/mW) needs 25.12 mW for the same peaks. A low-sensitivity headphone at any impedance is the real power hog.
Why do manufacturers use two different sensitivity standards?
Mostly history. Sennheiser publishes dB at 1 Vrms, Beyerdynamic publishes nominal SPL at 1 mW/500 Hz, and Audio-Technica and HIFIMAN publish a bare dB figure that the industry reads as dB/mW at 1 kHz. Always check which reference a spec uses before comparing two models - this calculator converts between the standards for you.
Is listening at 110 dB safe for my hearing?
No - 110 dB is a peak target for amplifier headroom, not a listening level. Sustained exposure above 85 dBA risks permanent hearing damage (NIOSH: 85 dBA for 8 hours, halving safe time for every 3 dB increase). Size your amp for 110 dB peaks, then listen with the volume far below that.
Where do the built-in headphone presets come from?
Each preset uses the manufacturer's published spec sheet: Sennheiser HD 600 (300 ohm, 97 dB at 1 V), Sennheiser HD 650 (300 ohm, 103 dB at 1 V), Audio-Technica ATH-M50x (38 ohm, 99 dB), Beyerdynamic DT 770 Pro 80 ohm (80 ohm, 96 dB nominal SPL at 1 mW), HIFIMAN Sundara (37 ohm, 94 dB). Specs change between revisions, so verify against your unit's datasheet for critical decisions.
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