The Vrms to dBm calculator allows you to convert an effective voltage (Vrms) applied to a characteristic impedance into power expressed in dBm.
This tool is useful for RF engineers and technicians to easily determine the strength of a signal from its voltage.
Formula used
P(W) = V rms 2 / R
dBm = 10 × log 10 (P(W) × 1000) = 20 × log 10 (V rms ) + 30 − 10 × log 10 (R)
Explanation
The first formula calculates the wattage from the effective voltage and impedance of the circuit.
The second formula converts this power into dBm, a logarithmic unit used to express power relative to 1 milliwatt.
V rms is the effective voltage in volts and R is the characteristic impedance in ohms.
Using the logarithm makes it easy to express large power ranges on a practical scale.
Calculation example
For an effective voltage V rms = 2 V applied to an impedance R = 50 Ω :
P(W) = 2² / 50 = 0.08 W
dBm = 10 × log 10 (0.08 × 1000) ≈ 19.03 dBm
Benefits and Use
- Quickly convert Vrms to dBm for analyzing RF signals.
- Useful for designing and testing RF circuits, amplifiers and antennas.
- Helps check power output and compare with component specifications.
- Facilitates RF system planning and signal measurement in varied environments.
