dBm to Voltage Calculator
Convert RF power (dBm) to RMS, peak, and peak-to-peak voltage across a known load impedance.
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Inputs
Live
Math
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Related
Enter parameters and click Calculate to view results
Formula & Theory
V(rms) = √(P(W) × R), where P(W) = 10^((P(dBm) - 30) / 10)This formula is used to calculate antenna parameters for dbm to voltage calculator.
Overview
The dBm to Voltage Calculator converts RF power levels expressed in decibel-milliwatts (dBm) into equivalent RMS voltage ($V_{\text{rms}}$), Peak voltage ($V_{\text{pk}}$), Peak-to-Peak voltage ($V_{\text{pp}}$), and $\text{dB}\mu\text{V}$ across any specified characteristic load impedance ($R$, typically $50\;\Omega$ or $75\;\Omega$).
Input Guide
Enter Power, Load Impedance (R) exactly in the units shown by this dbm to voltage. Check the operating band, unit prefix, and decimal position before calculating; these are the inputs used by the formula.
- Power — use dBm.
- Load Impedance (R) — use Ω.
Output Guide
The results describe the calculated dbm to voltage values for the inputs you entered. Check each value against the available space, selected components, feed system, and operating conditions before making a final design decision.
How This Calculator Works
The dBm to Voltage uses V(rms) = √(P(W) × R), where P(W) = 10^((P(dBm) - 30) / 10). Supply Power (dBm), Load Impedance (R) (Ω) in the displayed units, then use the calculated values as the first engineering target for this rf conversion design or analysis.
Design Notes
Power in dBm is referenced to $1\text{ milliwatt}$ ($0\text{ dBm} = 1\text{ mW}$). To convert power in dBm to RMS voltage, first convert dBm to linear Watts: $P_{\text{Watts}} = 10^{(P_{\text{dBm}} - 30)/10}$. RMS voltage is then calculated using Ohm's Law: $V_{\text{rms}} = \sqrt{P_{\text{Watts}} \cdot R}$. For a standard $50\;\Omega$ system, $0\text{ dBm}$ corresponds to exactly $0.2236\text{ V}_{\text{rms}}$ ($223.6\text{ mV}_{\text{rms}}$ or $632.5\text{ mV}_{\text{pp}}$) and $107\text{ dB}\mu\text{V}$.
Build and Tuning Notes
When connecting RF signal generators or power amplifiers to oscilloscopes and spectrum analyzers, always verify system load impedance ($50\;\Omega$ vs $75\;\Omega$). Measuring a $50\;\Omega$ source with a high-impedance ($1\;\text{M}\Omega$) oscilloscope probe doubles the displayed peak-to-peak voltage due to unloaded signal reflection ($+6\text{ dB}$ voltage scaling). Ensure proper inline $50\;\Omega$ feedthrough terminations are installed for high-frequency measurements.
Frequently Asked Questions
How do I convert 0 dBm to RMS voltage in a 50 Ω system?
$0\text{ dBm}$ equals $1\text{ mW}$ ($0.001\text{ W}$). In a $50\;\Omega$ load, $V_{\text{rms}} = \sqrt{0.001 \cdot 50} = \sqrt{0.05} \approx 0.2236\text{ V}_{\text{rms}}$ ($223.6\text{ mV}_{\text{rms}}$).
What is the relationship between Vrms, Vpeak, and Vpp for sinusoidal RF signals?
For pure sinusoidal AC signals, Peak Voltage is $V_{\text{pk}} = V_{\text{rms}} \cdot \sqrt{2} \approx 1.414 \cdot V_{\text{rms}}$. Peak-to-Peak voltage is $V_{\text{pp}} = 2 \cdot V_{\text{pk}} \approx 2.828 \cdot V_{\text{rms}}$.
How does load impedance (e.g., 50 Ω vs 75 Ω) change the voltage calculation?
Voltage depends on load resistance ($V = \sqrt{P \cdot R}$). For $0\text{ dBm}$ ($1\text{ mW}$), a $50\;\Omega$ load develops $223.6\text{ mV}_{\text{rms}}$, whereas a $75\;\Omega$ load develops $273.9\text{ mV}_{\text{rms}}$.
How is dBµV calculated from RMS voltage?
$\text{dB}\mu\text{V}$ expresses RMS voltage relative to $1\text{ microvolt}$ ($1\;\mu\text{V}$): $\text{dB}\mu\text{V} = 20 \cdot \log_{10}(V_{\text{rms}} / 1\mu\text{V}) = 20 \cdot \log_{10}(V_{\text{rms}} \cdot 10^6)$.
Alex Warren
B.Sc. in Electrical & Electronic Engineering (EEE)
Alex specialises in antenna design and wave propagation. His expertise helps ensure these calculators present practical RF concepts, useful design estimates, and clear engineering guidance for students, HAM operators, and wireless professionals.