Whether a phone or laptop can drive a pair of headphones depends on two specs: impedance (ohms) and sensitivity. Low-sensitivity, high-impedance headphones need more voltage, which small devices cannot supply. Aim for an amplifier output impedance under one-eighth of the headphone impedance for good damping. Listening at high levels for long periods damages hearing.
How to use the Headphone Power Calculator
- Impedance
- Sensitivity given as
- Sensitivity
- Target peak loudness
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the headphone impedance, its sensitivity in dB per mW or dB per V and the peak loudness you want (110 dB SPL covers loud peaks).
Tips
- Use the figures printed on your product or its manual when you have them.
- Round quantities up so you are never short.
- Measure twice before you buy anything cut to size.
- Everything runs in your browser – try different values to compare options.
Common mistakes to avoid
- Mixing units (inches and centimetres, mAh and Ah).
- Ignoring efficiency losses and safety margins.
- Treating rules of thumb as exact.
Inputs explained
| Field | What to enter |
|---|---|
| Impedance | In Ω |
| Sensitivity given as | Choose one: dB SPL per mW, dB SPL per V |
| Sensitivity | In dB |
| Target peak loudness | In dB SPL |
What each result means
- Power needed = 10^(([Target peak loudness] – [Sensitivity in dB÷mW])÷10)
- Voltage needed (RMS) = sqrt([Power needed]÷1000×[Impedance])
- Current needed (RMS) = [Voltage needed (RMS)]÷[Impedance]×1000
- Maximum amp output impedance = [Impedance]÷8
Example values
How the main result changes when Impedance changes and everything else stays at the example values above:
| Impedance (Ω) | Power needed (mW) |
|---|---|
| 16 | 10 |
| 24 | 10 |
| 32 | 10 |
| 40 | 10 |
| 48 | 10 |
| 64 | 10 |
Formula
Sensitivity (dB/mW) = sensitivity (dB/V) + 10 × log₁₀(impedance ÷ 1,000)Power (mW) = 10^((target dB − sensitivity dB/mW) ÷ 10)Voltage = √(power × impedance); current = voltage ÷ impedanceWorked example
Inputs — Impedance: 32 Ω; Sensitivity given as: dB SPL per mW; Sensitivity: 100 dB; Target peak loudness: 110 dB SPL.
Results — Sensitivity in dB/mW = 100; Power needed = 10 mW; Voltage needed (RMS) = 0.566 V; Current needed (RMS) = 17.68 mA; Maximum amp output impedance = 4 Ω.
Frequently asked questions
Do I need a headphone amp?
If the voltage needed is above about 0.5–1 V RMS or the power above 20–50 mW, most phones will struggle.
What is a good sensitivity?
Above about 100 dB/mW is easy to drive; below 90 dB/mW usually needs an amp.
Is 110 dB safe?
Only for brief peaks – average listening should stay well below 85 dB.
What formula does the Headphone Power Calculator use?
Sensitivity (dB/mW) = sensitivity (dB/V) + 10 × log₁₀(impedance ÷ 1,000).