• 🔊 Decibel Calculator

    Calculate decibels from power or amplitude ratios, convert a decibel value back into a ratio, or combine two sound levels using logarithmic decibel math.
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    Quick Decibel Reference

    dB Change Power Ratio Amplitude Ratio
    +3 dB ≈ 2× ≈ 1.41×
    +6 dB ≈ 4× ≈ 2×
    +10 dB 10× ≈ 3.16×
    +20 dB 100× 10×
    -6 dB ≈ 0.25× ≈ 0.50×
    How the Decibel Calculator works:

    Decibels describe a ratio using a logarithmic scale rather than a simple linear scale. The formula depends on what is being compared.

    For power quantities, the calculation uses 10 × log10(P2 ÷ P1).

    For compatible amplitude quantities such as voltage under the same impedance conditions, the calculation uses 20 × log10(A2 ÷ A1).

    Decibel levels also cannot normally be added using ordinary arithmetic. When combining independent sound levels, their underlying linear quantities must be added before converting the result back into decibels.

  • A Decibel Calculator helps musicians, audio engineers, producers, students, speaker builders, and sound enthusiasts calculate relationships between decibels, power, voltage, amplitude, and sound levels.

    Decibels use a logarithmic scale, so ordinary multiplication and addition do not always work the way you might expect. For power ratios, the calculation uses 10 × log10(P2 ÷ P1). For compatible amplitude quantities, such as voltage measurements under the same impedance conditions, the calculation commonly uses 20 × log10(A2 ÷ A1).

    For example, doubling power produces an increase of approximately 3 dB, while doubling voltage or another compatible amplitude quantity corresponds to approximately 6 dB under the appropriate conditions.

    The calculator can also work in reverse, converting a decibel change into its corresponding power or amplitude ratio.

    You can additionally combine two independent decibel levels. Because decibels are logarithmic, two 70 dB sound levels do not equal 140 dB. Under the assumptions used for independent sound-level addition, they combine to approximately 73 dB.

    Keep in mind that dB, dB SPL, dBFS, dBu, dBV, and other decibel-based units are not interchangeable. Each may use a different reference.

    Tip: Always identify what your decibel measurement is referencing before interpreting the number. A value such as -6 dBFS in digital audio describes something very different from 70 dB SPL measured acoustically in a room.

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