dB Attenuation Calculator

Calculator Inputs

Choose a solution mode, select the physical basis, then enter the known values. The result appears above this form after submission.

Scenario Label

Calculation Mode

Physical Basis

Voltage, current, and pressure use the 20·log10 form.

Input Level

Output Level

Attenuation (dB)

Output / Input Ratio

Unit Label

Safety Margin (dB)

Decimal Places

Formula Used

1) Attenuation from two levels
A_dB = K × log₁₀(L_in / L_out)

2) Output from input and attenuation
L_out = L_in × 10^{(-A_dB / K)}

3) Attenuation from ratio
A_dB = -K × log₁₀(r), where r = L_out / L_in

4) Factor selection
K = 10 for power and intensity.
K = 20 for voltage, current, and pressure ratios under equal-impedance assumptions.

This calculator also reports transmission ratio, percent loss, power ratio, amplitude ratio, and nepers to give a wider physics interpretation of the same attenuation result.

How to Use This Calculator

Select the calculation mode that matches your known values.
Choose the physical basis: power, intensity, voltage, current, or pressure.
Enter the input values, output values, dB value, or ratio as needed.
Set a unit label and optional safety margin for design checking.
Press Calculate Attenuation to display the result above the form.
Review the graph and export the summary using CSV or PDF.

Example Data Table

Case	Basis	Input	Output	Ratio	Attenuation
RF power link	Power	100 W	50 W	0.5000	3.0103 dB
Sensor voltage drop	Voltage	10 V	5 V	0.5000	6.0206 dB
Sound pressure reduction	Pressure	2 Pa	0.5 Pa	0.2500	12.0412 dB
Optical intensity filter	Intensity	80 W/m²	20 W/m²	0.2500	6.0206 dB

Frequently Asked Questions

1) What does dB attenuation mean?

dB attenuation expresses how much a signal decreases on a logarithmic scale. A positive attenuation value means output is smaller than input. Larger dB values indicate stronger loss.

2) Why does the calculator use 10 or 20 in the formula?

Power and intensity are energy-like quantities, so they use 10·log10. Voltage, current, and pressure are amplitude-like quantities, so they use 20·log10 when impedance stays consistent.

3) Can attenuation be negative?

Yes. A negative result means the output exceeds the input. In that situation, the system behaves like a gain stage rather than an attenuating one.

4) What is the transmission ratio?

The transmission ratio is output divided by input. A value of 0.5 means half the original level remains. The calculator converts that ratio into dB automatically.

5) Why is the voltage attenuation larger than power attenuation for the same numeric ratio?

Voltage and current use the 20·log10 relation. Power uses 10·log10. Therefore, a 0.5 voltage ratio becomes about 6.02 dB, while a 0.5 power ratio becomes about 3.01 dB.

6) What does the safety margin do?

The safety margin adds extra dB loss on top of the calculated attenuation. It helps with conservative design checks where real systems may suffer additional cable, connector, or environmental losses.

7) What are nepers in the result summary?

Nepers are another logarithmic attenuation unit used in physics and engineering. They are linked to natural logarithms. This calculator converts dB to nepers for wider technical reference.

8) Are the graph and export files based on the same result?

Yes. The graph, CSV file, and PDF summary are all generated from the same computed values shown in the result cards. That keeps reporting consistent across outputs.