Decibel Gain Calculator
Enter an input and output value to find the gain in decibels, or enter a decibel value to find the linear ratio. Voltage and other amplitude ratios use a factor of 20, while power ratios use a factor of 10.
How to use the decibel gain calculator
- Choose whether your values are a voltage (amplitude) ratio or a power ratio.
- Enter the input and output values, or switch to enter a decibel value.
- Read the gain in decibels and the linear ratio.
Examples
Voltage gain of 10
type = voltage, outputValue = 10, inputValue = 1
gain = 20.00 dB, ratio = 10
Power gain of 100
type = power, outputValue = 100, inputValue = 1
gain = 20.00 dB, ratio = 100
Frequently asked questions
What is the decibel voltage gain formula?
Voltage gain in decibels is 20 times the base-10 logarithm of the output over the input, gainDb = 20 * log10(Vout / Vin). A voltage ratio of 10 is 20 dB.
Why does power use 10 and voltage use 20?
Power is proportional to voltage squared, so the logarithm of a power ratio is twice that of the matching voltage ratio. That gives 10 * log10 for power and 20 * log10 for voltage.
How do I convert decibels back to a ratio?
Raise 10 to the decibel value divided by the factor, ratio = 10^(dB / 20) for voltage or 10^(dB / 10) for power. A voltage gain of 6 dB is a ratio of about 1.9953.
What does 3 dB mean?
A power gain of 3 dB is about a ratio of 2, which is why a doubling of power is often called a 3 dB increase. For voltage, a ratio of 2 is about 6 dB.
Can gain be negative?
Yes. When the output is smaller than the input the ratio is below 1 and the decibel value is negative, which represents attenuation or loss rather than gain.
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