Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Measured power (W)

Measured or output power level.

Reference power (W)

Reference or input power level.

Compute a power ratio in decibels, dB = 10 * log10(P2 / P1); a tenfold power increase is +10 dB. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Power ratio (dB)

Level of the measured power relative to the reference.

• Decibels express a ratio; the reference quantity and whether the ratio is power or a field quantity must be explicit. dBm, dBW, dBV, dBu, and dB SPL are not interchangeable, and impedance assumptions matter when converting voltage to power.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Decibel Voltage Ratio Calculator

  Compute an amplitude ratio in decibels across equal impedances, dB = 20 * log10(V2 / V1); a tenfold voltage increase is +20 dB.

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  Convert power-supply rejection ratio from voltage-ratio decibels to a linear rejection factor, 10^(PSRR/20). A 80 dB PSRR means a 10,000:1 small-signal voltage rejection at the stated frequency.

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  Compute the power supply rejection ratio in decibels as 20 x log10(delta Vsupply / delta Vout); both deltas must be positive.