Signal Power Converter
Free Signal power Converter for signal & frequency units. Enter a value to see equivalent measurements across systems. Get results you can export or share.
Formula
dBm = 10 * log10(P_mW) | P = V^2 / Z
Convert between linear power (watts) and logarithmic power (dBm, dBW) using decibel formulas. dBm uses 1 mW as reference, dBW uses 1 W. Voltage = sqrt(Power * Impedance).
Worked Examples
Example 1: WiFi Router Power Conversion
Problem: A WiFi router transmits at 20 dBm. Convert to watts and find the voltage across 50 ohms.
Solution: Power = 10^((20-30)/10) = 10^(-1) = 0.1 W = 100 mW\nVoltage RMS = sqrt(0.1 * 50) = sqrt(5) = 2.236 V\nCurrent RMS = sqrt(0.1 / 50) = 0.04472 A
Result: 20 dBm = 100 mW = 0.1 W | Vrms = 2.236 V at 50 ohms
Example 2: Cell Phone Signal Strength
Problem: A received signal measures -80 dBm. What is the power in watts?
Solution: Power = 10^((-80-30)/10) = 10^(-11)\nPower = 1e-11 W = 10 picowatts\ndBW = -80 - 30 = -110 dBW\nVrms = sqrt(1e-11 * 50) = 7.07e-5 V
Result: -80 dBm = 10 pW | -110 dBW | Vrms = 70.7 uV
Frequently Asked Questions
Why is impedance needed to convert between power and voltage?
Power, voltage, and current are related through impedance by the formulas P = V^2/Z and P = I^2*Z, where Z is the impedance. Without knowing the impedance, you cannot determine the voltage or current from power alone. Standard impedances in RF systems are 50 ohms (most test equipment and transmitters), 75 ohms (cable TV and video), and 600 ohms (traditional telephone lines). The choice of impedance affects signal levels significantly.
What are typical signal power levels in communications?
Signal power levels vary enormously across applications. WiFi routers transmit at about 20 dBm (100 mW). Cell phones transmit up to 23 dBm (200 mW) for 4G. FM radio stations broadcast at 50-100 kW (47-50 dBW). GPS satellite signals arrive at Earth at about -130 dBm (0.1 femtowatts). Cell tower receivers can detect signals as weak as -110 dBm. This vast range is why logarithmic units like dBm are essential in RF engineering.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
Can I share or bookmark my calculation?
You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.
How accurate are the results from Signal Power Converter?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
Does Signal Power Converter work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.