Most measurements on phones or laptops for signal strengths of Wi-Fi, 4G or 5G networks are negative dBm values.

**The reason for this is that the received signal power is less than one milliwatt. The dBm equivalent is negative for these power levels.**

**Detailed Explanation**

➡️ Most devices report received power levels in **dBm**. dBm is a logarithmic unit that expresses the power level relative to 1 milliwatt (mW).

**What is the relation between milliwatt and dBm?**

**P _{dBm}=10*Log_{10}(P_{mW})**

where

**P** is the power in dBm_{dBm}**P**is the power in milliwatts_{mW}

The calculator below gives the dBm equivalent of a power in mW.

**A value of 1 mW is equivalent to 0 dBm**

Any value greater than 1 mW will result in a positive dBm value. A value less than 1 milliwatt gives a negative dBm value.

- 10 milliwatt is equivalent to 10 dBm
- 0.1 milliwatt is equivalent to -10 dBm

Since most devices receive signals lower than 1 milliwatt, the reported power is a negative value in dBm units

**What does a negative dBm reading mean?**

A negative dBm reading means the received signal strength at the antenna of your wireless device (cellphone, laptop or tablet) is less than 1 milliwatt.

This is a weak signal when you consider that a milliwatt is one-thousandth of a watt.

However for a wireless device it is quite strong. A 0 dBm signal is very strong. In fact anything greater than -60 dBm is very good. Only a signal lower than -90 dBm is weak.