dB to V/V Formula and Calculator

This tool calculates the Voltage Ratio (V/V) from its deciBel (dB) value.

🔄 Voltage Ratio to dB

Formula

Voltage Ratio = V_ratio = V/V = 10^PdB/20

where PdB is the deciBel value of the voltage ratio

Notes

• These formulas assume the input and output impedances are the same.
• V_ratio is the ratio of two Root-mean-square voltage values (not the peak or average)
• Since RMS voltage is always positive, V_ratio is also always a positive number

Example Calculation

A ratio quantifies how many times one number contains another. For instance, a ratio of two voltages denoted V1:V2 = 5:1 means the voltage V1 is five times V2. Conversely V2 is one-fifth the value of V1. The voltage ratio is a linear value and has no units.

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

The calculator on this page converts from a the ratio to its deciBel equivalent.

• For a PdB value of 100 dB, the Voltage ratio is 100000 = 10⁵
• A PdB value of 1 dB gives a linear Voltage ratio of 1.12

dB values less than 0 dB have a ratio between 0 and 1. For instance, PdB = -10 dB gives a ratio of 0.316. The more negative the dB value, the closer to 0 the ratio.

Table of dB to Voltage Ratio

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

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• dB to Power Ratio