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RF Systems

RF Power, Voltage, and Current Converter

Convert dBm, mW, RMS voltage, current, dBμV, and dBμA at a specified impedance.

FORMULAv1.1.0
INPUT PARAMETERS

Convert within a specified impedance system

For matched, purely resistive RF systems. The default is 50 Ω, common in instruments and coaxial links.

CALCULATION RESULT

Calculation result

Calculated locally
∿

Enter the parameters and run the calculation to see results and model assumptions here.

FORMULA & TRACEABILITY

Formulas and applicability

Formulas, variables, and model boundaries are published. References last reviewed on 2026-08-30.

4 formulas · 2 references
CORE EQUATIONS

Core equations

These equations directly produce the primary results and define the tool’s core model.

2
F01

Power relationship for a resistive load

P = Vᵣₘₛ² / R = Iᵣₘₛ²R

For a matched resistive system, calculate average power from RMS voltage, current, and impedance.

P
Average powerW
Vᵣₘₛ
RMS voltageV
Iᵣₘₛ
RMS currentA
R
System impedanceΩ
Applicability
  • Steady-state sinusoidal RMS values
  • Purely resistive, matched load
F02

dBm power level

dBm = 10 log₁₀(P / 1 mW)

dBm is a power level referenced to 1 mW.

P
Average powermW
Applicability
  • Must be a power quantity; use 10 times the logarithm
DERIVED & CONVERSION

Derived and conversion equations

Derive units, levels, and supporting engineering quantities from the core values.

2
F03

dBμV and dBμA

dBμV = 20 log₁₀(V / 1 μV)；dBμA = 20 log₁₀(I / 1 μA)

Voltage and current are amplitude quantities; use 20 times the logarithm and state the reference.

V
RMS voltageV
I
RMS currentA
Applicability
  • Voltage and current are both RMS values
  • Reference quantities are 1 μV and 1 μA respectively
F04

Impedance-dependent level offset

dBμV = dBm + 90 + 10 log₁₀R

At 50 Ω the offset is 106.9897 dB, commonly approximated as 107 dB in engineering work.

R
System impedanceΩ
Applicability
  • Same matched resistive load
  • Do not use a fixed 107 dB offset outside a 50 Ω system
REFERENCES

References

01ITU-R · Recommendation SM.575-3Protection of fixed monitoring stations against nearby or strong transmitters2021 · Explicitly gives P(dBm) = U(dBμV) − 107 dB for a 50 Ω system.
02NIST · NIST SP 811NIST Guide to the SI, Chapter 8: Logarithmic quantities and units2008 (web edition updated) · Specifies 10 lg for power quantities and 20 lg for amplitude quantities, with the reference stated.
Engineering use notice

Results use the models and assumptions shown on this page for design estimates and pre-compliance risk review. Complex structures, dispersion, near-field coupling, and test setup can cause significant deviation.

FAQ

Frequently asked questions

How do dBm and dBμV convert in a 50 Ω system?

P(dBm) = U(dBμV) − 107 dB (exactly 106.9897 dB at 50 Ω). The offset is about 108.75 dB at 75 Ω—do not mix systems.

What is the dBm-to-watt formula?

P(mW) = 10^(dBm/10). 0 dBm = 1 mW, 30 dBm = 1 W, and every +3 dB doubles the power.

Why is 10·log used for power but 20·log for voltage?

Voltage and current are amplitude quantities; power is proportional to their square, so 10·log(P) corresponds to 20·log(U) within the same impedance system, with references stated explicitly.

PRE-COMPLIANCE SUPPORT

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