Calculate decibel

Convert level ratios to decibels, combine independent levels, or estimate inverse-square distance loss.

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ToolDecibel Calculator
Input
Output
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Preview

How it works

Power ratios use 10 log₁₀(P₂/P₁), amplitude ratios use 20 log₁₀(A₂/A₁), and independent levels combine by converting to linear power before summing. Distance mode applies the inverse-square 20 log₁₀(d₁/d₂) level change.

  • Power is the initial ratio quantity.
  • Absolute levels need a supplied reference; no microphone calibration is inferred.

Worked example

Two 70dB machines running together
Adding two independent sources of equal level
Input
											Mode: Combine two levels
Level adb: 70
Level bdb: 70
Combine operation: add
Output
												Combined level db: 73.0103
Level at target distance db: 0
Ratio value: 0
Mode used: Combine two levels

When to use this

Audio work compares signal levels, radio planning estimates distance loss, and measurement lessons combine independent power sources.

Edge cases

  • Adding 3 dB to power approximately doubles power, while amplitude ratios use a different logarithmic factor.
  • Subtracting a background that is not lower than the total is rejected.
  • 0 dB is a ratio of one, not silence or an absolute sound level without a reference.

References