Signal Strength Calculator
Convert wireless signal strength between dBm, milliwatts, and microwatts.
Inputs
dBm
-65.000dBm
Milliwatts
0.000000mW
Microwatts
0.000µW
Step by step
Values used
Input Unit = dBm; Value = -65
dBm to milliwatts
mW = 10^(dBm / 10)
Milliwatts to dBm
dBm = 10 × log10(mW)
dBm
= -65.000 dBm
Milliwatts
= 0.000000 mW
Microwatts
= 0.000 µW
How it works
dBm is a logarithmic power unit referenced to 1 milliwatt: dBm = 10·log10(power_in_mW). This logarithmic scale compresses the enormous dynamic range of wireless signal power (from nanowatts to watts) into a compact, easy-to-work-with number, and — since it's logarithmic — gains and losses along a signal path can simply be added or subtracted in dB rather than multiplied or divided, which is why link budgets are always computed in dBm/dB.
Formulas
dBm to milliwatts
mW = 10^(dBm / 10)
Milliwatts to dBm
dBm = 10 × log10(mW)
Frequently Asked Questions
Why use dBm instead of watts or milliwatts directly?
Wireless signal power spans many orders of magnitude, from picowatts of noise to watts of transmit power. The logarithmic dBm scale compresses this into small, manageable numbers, and critically, lets path losses and gains be added/subtracted rather than multiplied/divided.
What does 0 dBm equal?
0 dBm equals exactly 1 milliwatt (1 mW), since dBm is defined relative to that 1 mW reference.
Why is WiFi signal strength always shown as a negative dBm value?
Because received wireless signals are almost always weaker than 1 mW after traveling through air and obstructions, so their dBm value is negative — e.g. -50 dBm (strong) is about 10 microwatts, while -90 dBm (weak) is about 1 nanowatt.
How do I add two dBm power levels together?
You can't add dBm values directly — convert each to mW (or W) first, add the linear values, then convert the sum back to dBm. Only gains/losses expressed in dB (not absolute power in dBm) can be added or subtracted directly.