Headphone Power Calculator
Our headphone power calculator is an essential tool to find the power or voltage required to drive your new headphones.
It can be hard to find a headphone amplifier that fits your needs if you are not an audiophile or if you don't have a headphone amp calculator. Luckily, we have the perfect calculator for you.
We've paired this tool with a short text covering:
 How much power do headphones use?
 Do I need a headphone amp?
 What is headphone sensitivity?
 And every formula you need to do the calculation manually.
What is headphone impedance?
Let's start from the basics. Impedance, measured in ohms, represents the opposition to current in AC (alternating current) circuits. Therefore, a headphone with a higher impedance will generally require more power than one with a lower impedance. We can see this using Ohm's law:
where:
 $P$ — Power delivered to the headphones in watts (W);
 $V$ — Voltage in volts (V); and
 $\Omega$ — Headphone's impedance in ohms.
However, impedance is not the only factor to consider when selecting a suitable amplifier for your headphones. Let's see what sensitivity means now.
To learn more, check our electrical power calculator and Ohm's law calculator.
What is headphone sensitivity?
Headphone sensitivity refers to a headphone's loudness when driven by a given power or voltage. A headphone's sensitivity is expressed in dB SPL/mW (decibels of sound pressure level at one milliwatt) or dB SPL/V (decibels of sound pressure level at one volt).
When written using dB SPL/mW, the sensitivity describes how efficiently the headphones convert a onemilliwatt signal into an audible sound. That's why sometimes the term headphone efficiency is used instead.
💡 A headphone's sensitivity changes with frequency. This is called the frequency response of the headphones. Generally, sensitivity is rated at a frequency of 1 kHz.
You can convert between dB SPL/mW and dB SPL/mW using the following formula:
where $Ω$ is the headphone's impedance.
This is the exact conversion our headphone power calculator realizes, so you can input sensitivity using any of these units, and it will automatically convert to the other.
Now that you know what headphone sensitivity is, let's see how it can tell you if you need a headphone amplifier.
❓ What exactly are dB? Read our dB calculator and find out!
How much power do your headphones need? Do you need a headphone amp?
To find out how much power you need to power your headphones, we need to use the following formula:
where:
 $\text{loudness}$ — Refers to the sound level (in dB SPL);
 $P$ — Power required to run your headphones at a given sound level; and
 $dB(\text{mW})$ — Headphone's sensitivity in dB SPL/mW.
After doing this calculation or using our headphone power calculator, you'll need to check if your headphones are connected to a power source that is able to output enough power.
For that, read the amplifier's specifications and look up its power output at your headphone's impedance. If this value is greater than or equal to your result, the amplifier will most probably work well with your headphones.
You can use this formula to know how much power your headphones use, too, as long as they're plugged into an amplifier with enough power.
💡 As a rule of thumb, it is also recommended that the amplifier's impedance is less than 1/8th of your headphone's impedance to avoid sound quality losses. This is called impedance matching.
How to use our headphone power calculator / headphone amp calculator
To use this headphone power calculator, follow these steps:

Input your headphone's impedance.

Input your headphone's sensitivity. You can find this on the specifications sheet on the manufacturer's website along with its unit dB SPL(mW) or dB SPL(V). You only need to input the sensitivity in either of them, and our tool will fill the other automatically.

Input your desired loudness. The recommended value is 110 dB SPL.

Our calculator will then output the power, voltage, and current required to run your headphones.
FAQ
How do I make my headphones louder?
To make your headphones louder, you need to pair them with an amplifier capable of outputting enough power. For that:

Write down your desired loudness level in dB SPL.

Write down your headphone's impedance (Ω) and sensitivity (dB @ 1 mW).

Input these values into the following formula:
P = 10^[(loudnesssensitivity)/10]

Find an amplifier rated for this power output at your headphone's impedance. Make sure it is within your headphone's input limits to avoid damage.
Can I use 250 ohm headphones without an amp?
It depends. In general, 250 Ω (ohms) will require a headphone amplifier. However, this is also largely dependent upon the headphone's sensitivity. A pair of headphones with enough sensitivity (and a good frequency response) will not require an amplifier to work properly.
How much power do the Beyerdynamic DT 990 PRO need?
About 25 mW. The DT990 PRO has a sensitivity rating of 96 dB @ 1 mW and an impedance of 600 Ω. Using the power formula:
P = 10^[(loudnesssensitivity)/10] = 10^[(11096)/10]
results in 25.12 mW required to run at 110 dB SPL.