Decibel (dB) Calculator
Power Ratio to dB
dB = 10 × log₁₀(P2/P1)
Voltage Ratio to dB
dB = 20 × log₁₀(V2/V1)
dB to Power/Voltage Ratio
Convert dB value to power and voltage ratios
Watts to dBm / dBW
Convert power in watts to dBm and dBW
Formula
Power: dB = 10 × log₁₀(P2/P1) | Voltage: dB = 20 × log₁₀(V2/V1) | dBm = 10 × log₁₀(P_mW) | dBW = 10 × log₁₀(P_W)
Frequently Asked Questions
What is a decibel (dB)?
A decibel (dB) is a logarithmic unit used to express the ratio between two values, usually power or amplitude. For power: dB = 10 × log₁₀(P2/P1). For voltage/amplitude: dB = 20 × log₁₀(V2/V1). It is widely used in electronics, acoustics, and telecommunications.
What is the difference between dBm and dBW?
dBm is decibels relative to 1 milliwatt (0 dBm = 1 mW). dBW is decibels relative to 1 watt (0 dBW = 1 W). The relationship is: dBm = dBW + 30. For example, 1 W = 0 dBW = 30 dBm.
How do common dB values translate to ratios?
3 dB = 2× power (1.41× voltage), 6 dB = 4× power (2× voltage), 10 dB = 10× power, 20 dB = 100× power (10× voltage), -3 dB = half power, -10 dB = 1/10 power, -20 dB = 1/100 power.
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