In this post we convert a power level from Watt to deciBel (dB).

**Watt** is an absolute unit of power. **dB** is a relative measure. In this case we consider a reference power **P _{ref}** when converting Watt to dB. The input power

**P**is referenced to this value when making the calculation.

_{w} Use this calculator to convert Watt to dBm. dBm stands for deciBel relative to one milliwatt (*Note the ‘m’)*. Both Watt and dBm are absolute numbers.

**Calculator**

Enter

- Power in Watt
- Reference Power in Watt

The tool will calculate the dB value

**Formula**

**P _{dB}** is determined by the following formula:

**P _{dB} = 10*Log_{10} (P_{w}/ P_{R})**

Where

**P**is the power specified in Watt_{W}**P**is the reference power in Watt_{R}

**Example Calculation**

The picture below shows the sound power level in **dB** vs the sound power level in Watt **(W)**

In this case P_{R} = 10^{-12} Watt

- 1 Watt of power is equivalent to 120 dB
- 0.001 Watt of power is equivalent to 90 dB