dBm to Watts
P = 10^((dBm − 30) / 10)
Quick answer
This calculator solves P = 10^((dBm - 30) / 10) for Power. With Power (dBm) 0 dBm, the result is 1 mW. It solves in 2 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
dBm is an absolute power measurement referenced to 1 milliwatt (0.001W), making 0 dBm exactly equal to 1mW. Unlike plain dB which is a ratio, dBm gives you an actual power level. It is the standard unit in RF engineering, telecommunications, and fiber optics because it allows signal power levels spanning many orders of magnitude to be expressed as manageable numbers. The conversion subtracts 30 because 1mW = 10^(-3)W, and -3 in the exponent becomes -30 when scaled by the factor of 10 in the dB formula.
Variables
- dBm — Absolute power level referenced to 1mW
- P — Power in watts (W)
Practical Notes
Common reference points: 0 dBm = 1mW, 10 dBm = 10mW, 20 dBm = 100mW, 30 dBm = 1W, -30 dBm = 1µW. WiFi transmitters typically operate at 15-20 dBm (30-100mW). Cell towers transmit at 43-46 dBm (20-40W). The dBm scale is implicitly referenced to 50Ω impedance in RF systems and 600Ω in audio.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| dBm | Power (dBm) | dBm | dBm |
| W | Power | mW | µW, mW, W, kW |
Step by step
- 1. What you know: Power (dBm) 0 dBm
- 2. The relation: P = 10^((dBm - 30) / 10)
- 3. Substitute: dBm = 0 dBm
- 4. Result: Power = 1 mW
Worked examples
Minimum range
Given: Power (dBm) -2 dBm
Result: Power = 0.631 mW
Low range
Given: Power (dBm) -20 dBm
Result: Power = 10 µW
Typical
Given: Power (dBm) 0 dBm
Result: Power = 1 mW
High range
Given: Power (dBm) 30 dBm
Result: Power = 1 W
Maximum range
Given: Power (dBm) 0.3 dBm
Result: Power = 1.072 mW
Solving for each variable
Solve for Power
Power (dBm) -2 dBm → 0.631 mW
Solve for Power (dBm)
Power 100 µW → -10 dBm
How Power changes with Power (dBm)
| Power (dBm) (input) | Power (result) |
|---|---|
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
| 0 dBm | 1 mW |
The same result in other units
| Unit | Value |
|---|---|
| µW | 1000 |
| mW | 1 |
| W | 0.001 |
Embed this calculator
Paste this into any page. It keeps working when this page updates, and credits the source.
<iframe src="https://vbatpower.com/embed/dbm-watts/" width="100%" height="460" style="border:1px solid #1f2a37;border-radius:12px" loading="lazy" title="dBm to Watts"></iframe>
<p><a href="https://vbatpower.com/formulas/dbm-watts/">dBm to Watts</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate dBm to Watts?
Use P = 10^((dBm - 30) / 10). With Power (dBm) 0 dBm, Power works out to 1 mW.
What is the formula for dBm to Watts?
The formula is P = 10^((dBm - 30) / 10). dBm is an absolute power measurement referenced to 1 milliwatt (0.001W), making 0 dBm exactly equal to 1mW.
How do you find Power (dBm) when you know the other values?
Rearrange for Power (dBm): with Power 100 µW, Power (dBm) is -10 dBm.
What units does dBm to Watts use?
Power is shown in µW, mW, W. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Signal & dB formulas →Need more features?
Save calculations, import telemetry data, simulate battery discharge, and collaborate with your team.
Try the App