dBm / Watts / dBW
Power Converter
Convert between milliwatts, watts, dBm, and dBW. Enter any value and get all equivalent power representations instantly. Used dozens of times a day by working RF engineers.
Convert RF Power Units
dBm to Watts Conversion Table
The most commonly referenced power levels in RF engineering. Memorize the bold values and you can calculate any conversion mentally using the 3 dB / 10 dB rules.
| dBm | dBW | Watts | Milliwatts | Common Use |
|---|---|---|---|---|
| -30 | -60 | 0.000001 | 0.001 | Minimum detectable signal |
| -20 | -50 | 0.00001 | 0.01 | Weak received signal |
| -10 | -40 | 0.0001 | 0.1 | Typical mixer LO level |
| 0 | -30 | 0.001 | 1 | Reference: 1 milliwatt |
| 3 | -27 | 0.002 | 2 | Double power |
| 10 | -20 | 0.01 | 10 | Low-power transmitter |
| 20 | -10 | 0.1 | 100 | WiFi / cellular typical TX |
| 30 | 0 | 1 | 1,000 | Reference: 1 Watt |
| 33 | 3 | 2 | 2,000 | Cellular base station per carrier |
| 37 | 7 | 5 | 5,000 | Point-to-point radio |
| 40 | 10 | 10 | 10,000 | Satcom BUC |
| 43 | 13 | 20 | 20,000 | High-power amplifier |
| 50 | 20 | 100 | 100,000 | Broadcast / radar |
| 60 | 30 | 1,000 | 1,000,000 | 1 kW radar transmitter |
Why RF Engineers Use dBm
The decibel-milliwatt (dBm) is the standard power unit in RF engineering because it transforms power calculations from multiplication and division into simple addition and subtraction. In a signal chain with multiple amplifiers, filters, cables, and connectors, you simply add the gains and subtract the losses in dB to find the output power.
Conversion Formulas
dBm = 10 × log₁₀(P_mW)
dBW = 10 × log₁₀(P_W)
dBW = dBm - 30
Logarithmic to Linear:
P_mW = 10^(dBm / 10)
P_W = 10^(dBW / 10)
P_W = P_mW / 1000
The 3 dB and 10 dB Rules
Two mental math shortcuts that every RF engineer uses:
- 3 dB = double the power. If you know that 30 dBm = 1 W, then 33 dBm = 2 W, and 27 dBm = 0.5 W. Subtracting 3 dB halves the power.
- 10 dB = 10× the power. If 20 dBm = 100 mW, then 30 dBm = 1000 mW = 1 W. Subtracting 10 dB divides power by 10.
By combining these two rules, you can estimate any conversion. For example: 36 dBm = 30 dBm + 3 dB + 3 dB = 1 W × 2 × 2 = 4 W.
When to Use dBm vs. dBW
- dBm is standard for component-level specs (amplifier output, mixer drive level, receiver sensitivity) and bench-level test and measurement.
- dBW is preferred in satellite link budgets, radar range equations, and high-power system calculations where the numbers in dBm become large.
- Watts/mW are used when calculating thermal dissipation, heatsink requirements, DC power consumption, and regulatory power limits.
Frequently Asked Questions
How do you convert dBm to Watts?
P(W) = 10^(dBm/10) / 1000. For example, 30 dBm = 10^(30/10) / 1000 = 1 Watt. Quick shortcut: 0 dBm = 1 mW, every +10 dB multiplies power by 10, and every +3 dB doubles power.
What is dBm?
dBm is a unit of absolute power expressed in decibels relative to one milliwatt. It is the most commonly used power unit in RF engineering. 0 dBm = 1 mW. Unlike dB (which is a ratio), dBm represents an actual power level.
What is the difference between dBm and dBW?
Both are absolute power units in decibels. dBm is referenced to 1 milliwatt; dBW is referenced to 1 Watt. The conversion is: dBW = dBm - 30. So 30 dBm = 0 dBW = 1 Watt. dBm is more common in component-level work; dBW is used in satellite and high-power systems.
Why not just use Watts?
In an RF signal chain, power levels can span from picowatts (-90 dBm) to kilowatts (+60 dBm). Logarithmic units compress this enormous range into manageable numbers and convert multiplication/division into addition/subtraction, making system-level calculations much simpler.