dB to Voltage Calculator: Convert Gain to Volts

A dB to voltage calculator converts a voltage ratio or a voltage gain in decibels into a linear voltage ratio. Enter the decibel value and, if you want an output voltage rather than a ratio, the reference or starting voltage; the calculator returns the ratio and corresponding output voltage.

Formula

For two voltages measured across the same impedance, the decibel difference is dB = 20 log₁₀(V_out / V_in). Rearranging gives V_out / V_in = 10^dB/20, so V_out = V_in × 10^dB/20.

• dB is the voltage gain or loss, in decibels.
• V_in is the reference or starting voltage, in volts (V).
• V_out is the resulting voltage, in volts (V).
• Voltage ratio is V_out/V_in, a unitless quantity.

The calculator uses a default input of 1 V so the output voltage has the same numerical value as the ratio. Set the input to your actual starting voltage to calculate a different output. A dB value alone determines a ratio, not an absolute voltage.

Worked Example

Using the calculator defaults, dB = 6 and V_in = 1 V:

1. Calculate the exponent: 6 / 20 = 0.3.
2. Find the voltage ratio: 10^0.3 ≈ 1.9953.
3. Multiply by the input voltage: 1 V × 1.9953 = 1.9953 V.

Rounded to four decimal places, the result is a voltage ratio of 1.9953 and an output voltage of 1.9953 V. This corresponds to nearly twice the starting voltage; 6 dB is commonly treated as approximately a two-to-one voltage ratio.

How to Use a dB-to-Voltage Calculator

• Enter the decibel gain or loss. Use a positive number for an increase and a negative number for attenuation.
• Enter the starting voltage in volts. Convert millivolts to volts first: for example, 500 mV = 0.5 V.
• Read the voltage ratio and output voltage. The ratio has no unit; the output uses the same voltage unit as the input if you consistently substitute that unit.

For a known input and output voltage, you can also calculate the dB difference directly with 20 log₁₀(V_out/V_in). For example, doubling a voltage gives 20 log₁₀(2) ≈ 6.02 dB. Halving it gives about −6.02 dB.

Why Voltage Uses 20 Logarithms

The decibel is fundamentally a logarithmic way to express a ratio. For power, the definition is 10 log₁₀(P_out/P_in). When the same impedance applies, electrical power is proportional to voltage squared: P = V²/R. Substituting the squared voltage ratio into the power formula yields 10 log₁₀((V_out/V_in)²), which simplifies to 20 log₁₀(V_out/V_in).

That condition matters. If the input and output impedances differ, the power ratio cannot generally be inferred from the voltage ratio using the simple 20-log relationship. The calculator is for voltage gain relative to a reference, not a universal conversion between any two electrical measurements.

Positive and Negative Decibel Values

A positive dB value means the output voltage magnitude exceeds the reference voltage; zero dB means the two magnitudes are equal. A negative value means the output is smaller. The formula works for all finite positive voltage ratios, including values below one.

• +20 dB gives a voltage ratio of 10.
• 0 dB gives a ratio of 1.
• −20 dB gives a ratio of 0.1, or one tenth of the input voltage.
• −6 dB gives a ratio of about 0.501, close to half.

Decibels describe a magnitude ratio, not polarity or phase. A result of 2 V does not say whether a signal is inverted relative to its input, nor does it describe the shape of a waveform. Those details need separate information.

Common Mistakes and Limits

• Using 10 instead of 20: use 20 for a voltage ratio under the same-impedance assumption. The 10-log form applies directly to power ratios.
• Expecting dB to specify volts by itself: dB is relative. You need a reference voltage to get an absolute output.
• Mixing units: convert values to one unit before comparing them. A ratio is unchanged if both voltages use volts, millivolts, or another consistent unit.
• Confusing amplitude and power: doubling voltage across the same impedance is about +6.02 dB, while doubling power is about +3.01 dB.
• Rounding too early: keep extra digits in the ratio and round the final result to suit the measurement context.

The calculation is an ideal ratio conversion. It does not account for circuit loading, frequency response, noise, clipping, measurement uncertainty, or whether a source can deliver the calculated voltage into a particular load. Those depend on the equipment and circuit.

Frequently Asked Questions

How do I convert dB to voltage?
Calculate the voltage ratio as 10^dB/20. Multiply that ratio by the reference voltage to get the output voltage.

How many volts is 0 dB?
Zero dB means the output voltage equals the reference voltage. It is not one fixed number of volts unless the reference is specified.

What is the voltage ratio for 6 dB?
It is 10^6/20 ≈ 1.995, approximately a doubling of voltage.

Is dB the same as dBm?
No. dB expresses a ratio, while dBm expresses power relative to 1 milliwatt. Converting dBm to voltage requires additional information, including the load impedance and the measurement convention.

Can I use this for audio voltage?
Yes, for a voltage gain or loss when the compared voltages share the relevant impedance conditions. The result is a magnitude conversion and does not describe loudness, which also depends on other factors.

Related

• Ys VIII Switch 2 Edition Storage & Startup Checks
• Desert Detectors Codes: How They Work
• RAID Partition Recovery: How It Works & What to Do

in db | Voltage gain | dB | 6 | - | 
in vin | Input voltage | V | 1 | 0 | 
out ratio | Voltage ratio | - | 10 ^ (db / 20) | 4
out vout | Output voltage | V | vin * ratio | 4