Watt to dBm Converter
Power · unit-converter
Convert Watt to dBm with a fixed input and output unit, step-by-step formula line, and reference tables. Linear units use SI watt definitions; mechanical hp uses 550 ft·lbf/s; BTU/h uses the IT BTU; dBm/dBW are logarithmic relative to 1 mW and 1 W. The full Power Converter also includes PS/CV, TR, kVA/MVA, and ft·lb/s.
Calculator
From: Watt (w)
To: dBm (dbm)
About Watt
The watt is the SI unit of power (one joule per second). All linear units in this converter are defined by a fixed watt equivalent.
About dBm
dBm is a logarithmic power level relative to 1 mW: P(W) = 10^((dBm − 30)/10). It is standard in RF and telecommunications; it is not a linear multiple of the watt.
How to convert watts to decibels relative to 1 mw (dbm)
dBm/dBW are logarithmic power levels. P_W = 10^((dBm − 30) / 10), P_W = 10^(dBW / 10), and inverse mappings use 10 × log₁₀(·) with P_W > 0.
From Watt, multiply by 1 W per w to get watts, then apply the dBm formula (watts must be positive).
Examples
Example #1: Convert 10 w to dbm
10 w → 40 dbm
Example #2: Convert 30 w to dbm
30 w → 44.771213 dbm
Summary
To convert Watt to dBm, multiply by watts per w, then apply dBm: dBm = 10 × log₁₀(P_W × 1000), where P_W = value_w × 1. Watts must be positive.
Relationship context
You are converting between SI / decimal power (watts and prefixes) (Watts) and logarithmic RF levels (dBm) (Decibels relative to 1 mW (dBm)). Log units (dBm/dBW) use base-10 definitions relative to 1 mW or 1 W; linear units map through watts first, then to or from the selected log unit. Only strictly positive power in watts maps to a real dB power value.
Conversion tables
| Watt (w) | dBm (dbm) |
|---|---|
| 0.1 | 20 |
| 1 | 30 |
| 2 | 33.0103 |
| 3 | 34.771213 |
| 4 | 36.0206 |
| 5 | 36.9897 |
| 6 | 37.781513 |
| 7 | 38.45098 |
| 8 | 39.0309 |
| 9 | 39.542425 |
| Watt (w) | dBm (dbm) |
|---|---|
| 10 | 40 |
| 20 | 43.0103 |
| 30 | 44.771213 |
| 40 | 46.0206 |
| 50 | 46.9897 |
| 60 | 47.781513 |
| 70 | 48.45098 |
| 80 | 49.0309 |
| 90 | 49.542425 |
| 100 | 50 |