dB Gain Calculator

Calculator

Choose a signal type and an operation, then press Calculate.

Fields marked * are required for your chosen operation.

Signal type *

Power uses 10·log10, voltage/current use 20·log10.

Operation *

Pick the form that matches what you know.

Decimal places

Controls rounding across results and exports.

Input value *

Use a dot for decimals (e.g., 0.75).

Input unit

Unit options depend on signal type.

Output value *

Provide output when computing gain or input.

Output unit

Matched to input units by default.

Gain (dB) *

Positive for gain, negative for loss.

Linear ratio *

Power ratio or amplitude ratio (depends on type).

Input impedance (Ω)

Used for power‑equivalent calculations.

Output impedance (Ω)

Set equal impedances to compare pure amplitude gain.

Note: For voltage/current with different impedances, the displayed power‑equivalent gain may differ from the amplitude gain.

Example Data Table

Scenario	Inputs	Output	Gain (dB)	Linear Ratio
Power amplifier	Pin = 2 mW	Pout = 20 mW	10.0000	10.0000
Voltage gain	Vin = 0.2 V	Vout = 2 V	20.0000	10.0000
Attenuator	Pin = 1 W	Pout = 0.5 W	-3.0103	0.5000

Try these values in the calculator to verify your setup.

Formula Used

Power gain (dB): G = 10 · log10(Pout / Pin)
Voltage gain (dB): G = 20 · log10(Vout / Vin)
Current gain (dB): G = 20 · log10(Iout / Iin)
Ratio from dB: Pout/Pin = 10^(G/10) (power), Aout/Ain = 10^(G/20) (voltage/current)
dBm / dBW: dBm = 10·log10(P(mW)), dBW = 10·log10(P(W))
Power from voltage/current: P = V²/R and P = I²·R

Use absolute values for amplitude ratios if you only care about magnitude.

How to Use This Calculator

Select the signal type (Power, Voltage, or Current).
Choose an operation based on what you already know.
Enter the required fields (input/output, gain, or ratio).
For Voltage/Current, optionally set Rin and Rout to see power‑equivalent values.
Press Calculate. The result appears above the form.
Use Download CSV or Download PDF to export results.

If you use dBm inputs/outputs, the difference (output − input) equals gain in dB for power.