Headphone Power Calculator — Voltage & Current Requirements

It depends on sensitivity and target volume. Most efficient headphones (100+ dB/mW) need less than 10mW for comfortable listening at 85 dB. For peak levels of 110 dB with 100 dB/mW sensitivity, you need 10mW. Planar magnetics with 85 dB/mW sensitivity may need 300+ mW for the same level.

High-impedance headphones (250-600 ohms) need more voltage but less current. Low-impedance headphones (16-32 ohms) need less voltage but more current. This is why high-impedance headphones pair well with valve amps (high voltage) while low-impedance headphones suit portable devices (limited voltage).

Average listening at 75-85 dB SPL is safe for extended periods. Musical peaks can reach 100-110 dB. Audiologists recommend limiting exposure to 85 dB for 8 hours, 94 dB for 1 hour, or 100 dB for 15 minutes. The WHO recommends keeping daily exposure below 85 dB.

Most phones output about 1V maximum into high impedance. For 300-ohm headphones at 100 dB/mW sensitivity, 1V delivers 3.33 mW (P = V²/Z = 1²/300) which is +5.2 dB over the 1 mW figure, giving about 105 dB — enough for most listening. But headroom for peaks may be limited. A dedicated amplifier is recommended for headphones above 150 ohms.