dB to Power Ratio

This tool calculates the Power Ratio from its deciBel (dB) value.

???? Power Ratio to dB

Formula

Power Ratio = 10^PdB/10

Example Calculation

A ratio quantifies how many times one number contains another. For instance, a ratio of two powers denoted P1:P2 = 3:1 means the power P1 is three times P2. Conversely P2 is one-third the value of P1. The power ratio is a linear value and has no units.

deciBel or dB expresses the ratio between two amplitude values on a logarithmic scale. It is useful for representing both large and small numbers.

The calculator on this page converts from the deciBel value (PdB) to an equivalent ratio.

Here are some examples:

• For a PdB value of 100 dB, the Power ratio is 10000000000 = 10¹⁰
• A PdB value of 1 dB gives a linear Power ratio of 1.26

PdB values less than 0 dB have a power ratio between 0 and 1. For instance, PdB = -10 dB gives a ratio of 0.1. The more negative the dB value, the closer to 0 the ratio.

Notes

• dB values can be positive or negative. In radio frequency systems, a positive value represents signal gain while a negative value represents signal attenuation.
• RF component value specifications for gain, noise figure and dynamic range for example are always specified in dB. This makes it easier to compute the total gain in a signal chain for example. An amplifier with a gain of 20 dB connected to a 3 dB attenuator will give 17 dB of net gain.
• dB can also be converted to a % value. A 3 dB gain gives a power ratio of 2 or a signal that’s amplified by 200%.

Table of dB to Power Ratio

This table presents linear equivalent over the range -100 dB to +100 dB.

References

• Ratio on Wikipedia
• dB on Wikipedia

Related Calculators

dB to Voltage Ratio