Decibel (dB) Converter
Convert decibel levels to and from their linear quantities and ratios for Sound Pressure Level (dB SPL), Voltage (dBV / dBu) and Power (dBm / dBW). Enter a value in any unit and read the equivalents, with the formulas and common reference levels.
Input
Reference Type
Output
Equivalent Values
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Common Reference Levels
| Source | Level |
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Guides
The Decibel (dB) Converter turns a decibel figure into the physical quantity behind it — and back again — across the three domains where decibels are used every day: sound pressure level (dB SPL), voltage (dBV / dBu) and power (dBm / dBW). Enter a value in any unit and instantly read every equivalent, along with the exact formulas and a table of familiar real-world reference levels.
Decibels are logarithmic, which is what makes them so easy to misread: +6 dB is roughly double the voltage, +3 dB is roughly double the power, and +20 dB SPL is ten times the sound pressure. This tool does the log and antilog arithmetic for you, so you can move between "how many dB" and "how many pascals / volts / watts" without reaching for a calculator.
How to use it
- Pick a Reference Type — Sound Pressure Level, Voltage or Power.
- Choose the Unit of the value you already have (for SPL that might be dB SPL, pascals, a pressure ratio or an intensity ratio).
- Type the Value. Results update as you type.
The Equivalent Values table shows the value expressed in every related unit and ratio for that domain. The Formulas panel lists the equations used, and Common Reference Levels gives you anchor points — a whisper, a rock concert, a Wi-Fi router's transmit power — to sanity-check your number.
What is the difference between dBV and dBu?
Both describe voltage on a logarithmic scale, but they use different 0 dB references. dBV is referenced to 1 volt, while dBu is referenced to about 0.7746 volts (the voltage that dissipates 1 mW into 600 Ω). That is why the professional "+4 dBu" line level and the consumer "-10 dBV" level are closer in actual voltage than the numbers suggest — the tool shows both side by side.
How are dBm and dBW related?
Both measure power. dBm is referenced to 1 milliwatt and dBW to 1 watt, so they always differ by exactly 30: dBm = dBW + 30. A 20 dBm Wi-Fi radio therefore transmits at -10 dBW, which is 0.1 W (100 mW).
Why is dB SPL calculated with 20·log₁₀ but power with 10·log₁₀?
Sound pressure and voltage are amplitude quantities, and power scales with the square of amplitude. Taking 20·log₁₀ of a pressure or voltage ratio gives the same decibel figure as 10·log₁₀ of the corresponding power or intensity ratio — the tool reports both the amplitude ratio and the power/intensity ratio so the relationship is visible.
What reference does dB SPL use?
The standard threshold of human hearing: p₀ = 20 µPa (20 micropascals). 0 dB SPL is that reference pressure; normal conversation sits near 60 dB SPL, and the threshold of pain is around 130 dB SPL.
Privacy
Every calculation runs entirely in your browser. Your values are never uploaded, logged or sent to a server — nothing leaves your device.