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Voltage to power conversion

Convert between Vpp, Vp, Vrms, dBm, mW, and W for a given impedance.

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Voltage to power conversion

Assumes a sine wave and a purely resistive load.

Vpp —
Vp —
Vrms —
dBm —
mW —
W —

Formulas used

  • Vrms = Vpp ÷ (2√2)
  • Vrms = Vp ÷ √2
  • Vpp = 2 × Vp
  • P (W) = Vrms² ÷ Z
  • P (mW) = P (W) × 1000
  • dBm = 10 × log₁₀(P in mW)

Frequently asked questions

How do you convert Vrms to dBm?

Convert the RMS voltage to power with P = Vrms² / R for the load impedance R, then dBm = 10 × log₁₀(P / 1 mW). Into 50 Ω, 1 Vrms is about 13.01 dBm.

What is the relationship between Vpp, Vp, and Vrms for a sine wave?

For a sine wave, Vp = Vpp / 2 and Vrms = Vp / √2 ≈ 0.707 × Vp.

Why does the impedance matter?

Power depends on the load because P = V² / R. The same voltage delivers different power into 50 Ω versus 75 Ω, so the impedance must be set correctly for the dBm and watt results.