Formulas: Power ratio in dB = 10×log₁₀(P2/P1). Voltage/current ratio in dB = 20×log₁₀(V2/V1) — the ×2 factor exists because power ∝ V², so a voltage ratio needs double the log-multiplier to represent the same power change. Reverse: P2 = P1×10^(dB/10), V2 = V1×10^(dB/20). Only valid for voltage/current ratios measured across the same impedance — otherwise use the power-ratio form directly.