dB Loudness Calculator
dB Conversion
Show the math
Compare Two Levels
Power ratio = 10^(dB/10); amplitude ratio = 10^(dB/20). A +10 dB rise is roughly twice as loud to human ears. Related: note frequency, reverb time.
What Your Result Means
- Absolute value: The physical quantity (pressure in pascals, voltage in volts, or power in watts) that corresponds to your dB reading, given the chosen reference level.
- Power ratio: How many times greater (or smaller) the signal power is compared to the reference. A 10 dB increase means 10× the power; 20 dB means 100×.
- Amplitude ratio: The voltage or pressure multiplier. Because power is proportional to amplitude squared, a 20 dB increase doubles the power ratio exponent but only means 10× the amplitude.
- Perceived loudness change: A rough psychoacoustic estimate. Humans generally perceive a 10 dB increase as "twice as loud," though perception varies with frequency and duration.
How This Calculator Works
You enter a decibel value and select a reference standard. The tool applies the standard decibel formulas: power ratio = 10^(dB/10) and amplitude ratio = 10^(dB/20). It then multiplies the reference level by the amplitude ratio to get the absolute physical value. The comparison card subtracts two dB levels and converts the difference to a power ratio and an approximate perceptual multiplier.
Quick Questions
What is the difference between dBSPL, dBV, dBu, and dBm?
Each uses a different reference point. dB SPL references 20 micropascals (the threshold of human hearing). dBV references 1 volt. dBu references 0.775 volts (the voltage that produces 1 mW across 600 ohms). dBm references 1 milliwatt of power.
Why does 10 dB not sound "10 times louder"?
Decibels measure physical power on a logarithmic scale, not perceived loudness. A 10 dB increase is 10× the power but roughly 2× the perceived loudness. Human hearing is approximately logarithmic, which is why the dB scale exists.
Can I use negative dB values?
Yes. Negative decibels mean the signal is below the reference level. For example, −6 dB SPL means the sound pressure is about half the reference pressure, well below the threshold of hearing.
How accurate is the perceived loudness estimate?
It is a rough approximation. True loudness perception depends on frequency (Fletcher-Munson curves), duration, and individual hearing. For critical audio work, use A-weighted measurements and calibrated equipment.
What dB level is dangerous to hearing?
Prolonged exposure above 85 dB SPL can cause hearing damage. Sounds above 120 dB SPL can cause immediate pain, and 140 dB SPL can cause instant permanent damage. Always use hearing protection in loud environments.
Sources
- Wikipedia — Decibel (dB definition, power vs. amplitude formulas, reference levels)
- CDC — What Is Noise? (safe exposure levels and hearing damage thresholds)
- Wikipedia — Equal-Loudness Contour (Fletcher-Munson curves and perceived loudness)
Method & review
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.