🎧 Headphone Power Calculator

How Much Power Do Your Headphones Need?

Enter the sensitivity (dB/mW from the spec sheet), impedance in ohms, and your target loudness, and the calculator returns the required power in milliwatts plus the voltage and current behind it. A 100 dB/mW, 32-ohm headphone hitting 110 dB SPL needs 10 mW: 0.57 volts and 17.7 mA. For just 100 dB, the same headphone needs only 1 mW.

The Formulas

Decibels are logarithmic, so every 10 dB needs ten times the power: 100 to 110 dB is 1 to 10 mW, and 120 dB would be 100 mW. Voltage follows from power and impedance via Ohm's law relations. High-impedance headphones (250-600 ohms) need more voltage but less current; low-impedance planars need current instead.

Worked Example

Sensitivity 100 dB/mW, impedance 32 ohms, target 110 dB: power = 10^((110-100)/10) = 10 mW. Voltage = sqrt(0.010 W x 32) = 0.57 V. Current = 0.57/32 = 17.7 mA. Any phone drives this easily. A 300-ohm headphone at 97 dB/mW targeting 110 dB needs 20 mW at 2.45 V: now you are shopping for an amplifier.

dB/mW vs dB/V Sensitivity

Specs quote one or the other, and they are not interchangeable without impedance. Convert: dB/V = dB/mW + 10xlog10(1000/impedance). For 32 ohms that is +14.9 dB. If your spec is in dB/V, convert first or the power figure will be wrong. When in doubt, check which unit the manufacturer printed.

For informational purposes only. Protect your hearing: prolonged listening above 85 dB can cause permanent damage. Keep volumes moderate.

Do You Need an Amplifier?

If the required voltage is under ~1 V and current under ~30 mA, a phone or laptop suffices. Past that, a dongle DAC or desktop amp earns its keep: not for "warmth" but for clean headroom at your target loudness. Buy power for the numbers, not for mythology.

Safe Listening Levels

The 110 dB target here is for brief peaks with headroom, not sustained listening: 85 dB for 8 hours is the commonly cited safe limit, and every 3 dB halves the safe time. If your normal listening needs more than a few milliwatts, turn it down before buying a bigger amp.

Balanced vs Single-Ended Power

Balanced outputs typically deliver about four times the power of single-ended from the same device, which matters for power-hungry headphones: a 300-ohm headphone needing 2.45 V might get it balanced but not single-ended. For efficient headphones the difference is inaudible headroom you will never use. Match the output to the numbers above: buy balanced for voltage-hungry loads, not as a general upgrade.

Balanced vs Single-Ended Power

Balanced outputs typically deliver about four times the power of single-ended from the same device, which matters for power-hungry headphones: a 300-ohm headphone needing 2.45 V might get it balanced but not single-ended. For efficient headphones the difference is inaudible headroom you will never use. Match the output to the numbers above: buy balanced for voltage-hungry loads, not as a general upgrade.

Worked Example: The Planar Magnetic

A planar magnetic headphone: 93 dB/mW sensitivity, 50 ohms, target 110 dB for orchestral peaks. Power needed: 10^((110-93)/10) = 10^1.7 = 50.1 mW. Voltage: sqrt(0.0501 x 50) = 1.58 V. Current: 1.58 / 50 = 31.6 mA. A phone's ~1 V output cannot get there, so this headphone needs an amplifier, no debate. The same target on a high-sensitivity conventional headphone needs a fraction of a volt, which is why sensitivity specs decide the amp question, not impedance alone.

The 110 dB target includes headroom: music peaks run 15 to 20 dB above the average level, so an amp that merely reaches your listening volume will clip the peaks. Size for the peaks, listen at the average.

Dongle DACs: The $10 Upgrade That Fixed Phones

When phones dropped the headphone jack, the $9 USB-C dongle DAC became the most cost-effective audio upgrade in history. The well-known ones measure flat and clean, audibly transparent for easy-to-drive headphones, outperforming the built-in audio of many laptops. For most earbuds and efficient headphones, the dongle is the entire chain: phone, dongle, music.

Step up to a real amplifier when the calculator says so: high-impedance dynamics (300 ohm) or insensitive planars need voltage and current the dongle cannot produce. Balanced 4.4 mm outputs roughly double the voltage swing of single-ended, which is why balanced amps drive hungry headphones louder from the same battery. Buy the amp the math requires, not the one the forums admire.

Worked Example: 300-Ohm Headphones at 110 dB

High-impedance studio headphones: 300 ohms, sensitivity 97 dB/mW. Target listening level 110 dB peak (loud, with headroom). Needed gain above 1 mW: 110 - 97 = 13 dB, which is a power ratio of 10^(13/10) = 20x, so 20 mW. Voltage = sqrt(0.020 x 300) = 2.45 V RMS. A phone dongle delivering 1 V RMS gives only 3.3 mW into 300 ohms, reaching about 102 dB: fine for moderate listening, short of the 110 dB target. This is the math behind "my phone can't drive these."

Compare easy-to-drive earbuds: 16 ohms, 105 dB/mW, target 100 dB. Needed: 10^((100-105)/10) = 0.32 mW. Voltage = sqrt(0.00032 x 16) = 0.07 V. Any phone delivers that with room to spare, which is why IEMs never need an amp. The calculator runs both directions: given your headphones and target loudness, it tells you the voltage and power required, and you compare against your source's specs.

dB/mW vs dB/V Sensitivity

Manufacturers quote sensitivity two ways and they are not interchangeable. dB/mW is power sensitivity: loudness at 1 milliwatt input. dB/V is voltage sensitivity: loudness at 1 volt input. For high-impedance headphones the dB/V number looks flattering because 1 volt into 300 ohms is only 3.3 mW. Convert between them: dB/V = dB/mW + 10 x log10(1000/impedance). A 97 dB/mW, 300-ohm headphone is 102.2 dB/V. Always convert to the same basis before comparing two models, or the comparison is meaningless.

The practical rule: if the math says you need under 1 V RMS, any modern phone or laptop suffices. Between 1 and 2 V, a decent USB dongle DAC covers it. Above 2 V into high impedance, you are in dedicated amplifier territory. Buying a $300 amp for headphones that need 0.5 V buys nothing but a volume knob you will never turn past nine o'clock.