Calculator Form
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Formula Used
dB = 10 × log10(linear / reference)dB = 20 × log10(linear / reference)dB = k × log10(linear / reference)The reference value defines the comparison baseline. A ratio of 1 returns 0 dB. Ratios above 1 create positive dB values, while ratios below 1 create negative dB values.
For reverse checking, use linear = reference × 10^(dB / factor). This page shows that back-converted value after each calculation.
How to Use This Calculator
- Select the quantity model that matches your physics problem.
- Enter the measured linear value.
- Enter the reference value, or keep it at 1.
- Use a custom multiplier only when your method needs one.
- Add optional batch values to build a comparison chart.
- Press Convert to dB to view the result above the form.
- Export the summary table with the CSV or PDF buttons.
Example Data Table
| Example | Model | Linear Value | Reference | Ratio | Result |
|---|---|---|---|---|---|
| Signal Power Gain | Power Ratio | 10 | 1 | 10 | 10.0000 dB |
| Voltage Gain | Amplitude Ratio | 2 | 1 | 2 | 6.0206 dB |
| Attenuation Case | Power Ratio | 0.5 | 1 | 0.5 | -3.0103 dB |
| Field Strength Change | Amplitude Ratio | 5 | 2 | 2.5 | 7.9588 dB |
| Custom Log Scale | Custom Factor 15 | 4 | 1 | 4 | 9.0309 dB |
Frequently Asked Questions
1. What does a linear to dB conversion mean?
It converts a plain ratio into a logarithmic decibel value. This makes very large or very small changes easier to compare in physics, electronics, acoustics, and signal analysis.
2. Why do some formulas use 10 and others use 20?
Power ratios use 10 because power is directly proportional to the ratio. Voltage, current, and field quantities use 20 because power is proportional to the square of those amplitudes.
3. Can the linear value be smaller than the reference?
Yes. When the linear value is lower than the reference, the ratio becomes less than one, and the computed decibel result becomes negative. That indicates attenuation or reduction.
4. Why is the reference value important?
Decibels describe a comparison, not an isolated absolute number. The reference sets the baseline. Changing the reference changes the ratio, and that changes the decibel output.
5. Can I enter zero as the linear value?
No. The logarithm of zero is undefined, so a valid linear input must always be greater than zero. The same rule applies to the reference value.
6. Is dB a physical unit like volts or watts?
Not exactly. Decibel is a logarithmic ratio expression. It tells you how much one value differs from a reference, rather than describing a standalone physical quantity by itself.
7. How do I convert dB back into a linear value?
Use the inverse relation: linear = reference × 10^(dB / factor). The factor is 10 for power ratios, 20 for amplitude ratios, or your custom multiplier.
8. When should I use the custom multiplier option?
Use it when your workflow follows a specialized logarithmic scaling rule. For standard physics and engineering tasks, power and amplitude modes are usually the correct choices.