Headphone Impedance Calculator
Knowing whether your phone, laptop, or dedicated DAC can properly drive your headphones requires understanding two key specifications: impedance and sensitivity. Impedance (measured in ohms) determines how much voltage the amplifier must supply; sensitivity (measured in dB per milliwatt) determines how much power is needed to reach a comfortable listening level. High-impedance headphones (>80 ohm) draw less current but need more voltage, which many portable devices cannot deliver. Low-impedance headphones draw more current and are generally easier to drive from smartphones and laptops, but they can be sensitive to the output impedance of the source device, causing frequency response coloration if the output impedance is not sufficiently low. This calculator takes your headphone's impedance and sensitivity rating and your target listening level to compute the required power in milliwatts and the required output voltage in volts. It then checks whether a typical smartphone headphone jack (rated at approximately 30 mW into 32 ohms, or about 1 volt RMS) is sufficient to drive your headphones to the target level. If not, a dedicated headphone amplifier or DAC/amp is recommended. Enter your headphone specifications below to get an instant assessment.
How headphone power and voltage requirements are calculated
Headphone sensitivity (dB/mW) relates sound output to electrical input. From the target SPL and the sensitivity rating, we can calculate the power needed. Voltage follows from Ohm's law applied to the headphone's impedance.
Power needed (mW) = 10 ^ ((target_SPL - sensitivity_dBmW) / 10)
Voltage needed (V) = sqrt(power_mW / 1000 x impedance_ohms)
Phone sufficient if power_needed <= 30 mW
Worked example
Impedance 32 ohms, sensitivity 100 dB/mW, target SPL 85 dBSPL:
- Power = 10 ^ ((85 - 100) / 10) = 10 ^ (-1.5) = 0.032 mW
- Voltage = sqrt(0.032 / 1000 x 32) = sqrt(0.000001024) = 0.0010 V (1.0 mV)
- 0.032 mW is well below 30 mW: phone jack is sufficient
By contrast, 300-ohm headphones with 103 dB/mW sensitivity at the same 85 dBSPL target need about 0.050 mW and 0.0039 V, which is still easily within phone capability. However, if sensitivity is lower (say 94 dB/mW), power requirements rise to 0.79 mW and voltage to 0.049 V, and a phone output near its noise floor may struggle with adequate dynamic range.
Common headphone types reference
| Type | Typical impedance | Typical sensitivity | Amp needed? |
|---|---|---|---|
| Smartphone earbuds | 16 to 32 ohms | 105 to 115 dB/mW | No |
| Consumer over-ear | 32 to 64 ohms | 95 to 105 dB/mW | Usually no |
| Studio monitor | 80 to 250 ohms | 95 to 102 dB/mW | Often yes |
| Audiophile planar | 20 to 100 ohms | 90 to 96 dB/mW | Yes |
| High-impedance reference | 250 to 600 ohms | 97 to 104 dB/mW | Yes |
Headphone impedance: frequently asked questions
What is headphone impedance and why does it matter?
Impedance is the AC resistance of a headphone's voice coil, measured in ohms. Low-impedance headphones (16 to 32 ohms) are easy to drive and work well with portable devices such as phones and laptops. High-impedance headphones (150 to 600 ohms) require more voltage from the amplifier to reach sufficient loudness, but they often benefit from lower noise floors and better channel separation in dedicated headphone amplifiers. Matching your headphone impedance to your source device's output impedance is important: a mismatch can cause frequency response errors and poor channel balance.
What is headphone sensitivity and how is it measured?
Headphone sensitivity is measured in decibels of SPL produced per milliwatt of input power (dB/mW). A headphone rated at 100 dB/mW produces 100 dB of sound pressure at your eardrum when driven with 1 milliwatt. Higher sensitivity means the headphone is easier to drive. Note that some manufacturers quote sensitivity as dB/V (per volt) rather than dB/mW, which gives different numbers for different impedances. This calculator uses dB/mW, which is the more informative measure for comparing headphones of different impedances.
Can a typical smartphone drive high-impedance headphones?
Most smartphones have headphone outputs rated at around 30 mW into 32 ohms, corresponding to a maximum output voltage of roughly 1 volt RMS. For 300-ohm headphones such as the Sennheiser HD 650, the same 1 V output delivers only about 3.3 mW, and the output stage may not be designed to maintain that voltage into a high load. The result is insufficient volume and potentially audible distortion. High-impedance headphones generally need a dedicated headphone amplifier or a DAC/amp with a sufficiently high voltage output.
What is a balanced headphone output and does it help?
A balanced output uses separate amplifier circuits for the positive and negative legs of each channel, effectively doubling the voltage swing available compared to a single-ended output. This means four times the power into the same load (power scales with voltage squared). Balanced connections use 4-pin XLR, 4.4 mm Pentaconn, or 2.5 mm TRRS connectors rather than the standard 3.5 mm TRS. For difficult headphones with high impedance or low sensitivity, a balanced output can make a significant practical difference. Many portable DAC/amp units now include balanced outputs.
What is the difference between low-impedance and high-impedance headphones in terms of sound quality?
High-impedance headphones are not inherently better-sounding, but they are more common among studio reference designs (e.g., 250 to 600 ohms) because they were historically easier to drive from professional mixing desks with high output impedance. Low-impedance headphones are better suited to portable use. Within a given headphone line, impedance often correlates with driver design choices rather than sound quality. The most important factor is matching the headphone to an appropriate amplifier with low output impedance (ideally less than one-eighth of the headphone's own impedance) to avoid frequency response coloration.
Official sources
- IEC 61938: Audio/video, musical instrument, and arts equipment (interconnections): IEC.ch.
- IEC 60268-7: Sound system equipment - headphones and earphones: IEC.ch.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. General information only.