Convert between decibels, power ratios, and voltage ratios. Combine sound levels, compare intensities, and explore dB scales.
The decibel (dB) is a logarithmic unit used to express the ratio between two values of a physical quantity, most commonly power or intensity. Because human hearing spans an enormous range—from the faintest whisper at about 10⁻¹² W/m² to the threshold of pain at roughly 1 W/m²—a logarithmic scale compresses this trillion-fold range into a manageable 0–130 dB scale.
This decibel calculator handles all common dB operations: converting between dB and linear ratios, computing power and voltage ratios, combining multiple sound sources, and comparing sound levels against common references. Whether you're working in audio engineering, acoustics, telecommunications, or electronics, this tool provides instant conversions and intuitive visualizations.
The calculator supports both the power convention (10·log₁₀ for power, intensity, energy) and the amplitude convention (20·log₁₀ for voltage, pressure, field strength). It also demonstrates key dB rules: +3 dB doubles power, +10 dB sounds twice as loud, and combining two equal sources adds exactly 3 dB.
Decibel calculations involve logarithms that are easy to get wrong, especially when combining multiple sources or converting between power and amplitude. This calculator handles all the math instantly and provides visual comparisons against common sound levels for intuitive understanding. The note above highlights common interpretation risks for this workflow. Use this guidance when comparing outputs across similar calculators. Keep this check aligned with your reporting standard.
Power ratio to dB: dB = 10 × log₁₀(P₂/P₁) Voltage ratio to dB: dB = 20 × log₁₀(V₂/V₁) Combining sources: dB_total = 10 × log₁₀(10^(dB₁/10) + 10^(dB₂/10)) N identical sources: dB_total = dB_single + 10 × log₁₀(N) Sound intensity: I = 10⁻¹² × 10^(dB/10) W/m²
Result: Combined: 80.04 dB, Power ratio: 1,000,000×
Combining 60 dB and 80 dB gives approximately 80.04 dB. The 80 dB source dominates because it carries 100 times more power. 60 dB alone represents a power ratio of 1,000,000× relative to the hearing threshold.
Use consistent units, verify assumptions, and document conversion standards for repeatable outcomes.
Most mistakes come from mixed standards, rounding too early, or misread labels. Recheck final values before use. ## Practical Notes
Use this for repeatability, keep assumptions explicit. ## Practical Notes
Track units and conversion paths before applying the result. ## Practical Notes
Use this note as a quick practical validation checkpoint. ## Practical Notes
Keep this guidance aligned to the calculator’s expected inputs. ## Practical Notes
Use as a sanity check against edge-case outputs. ## Practical Notes
Capture likely mistakes before publishing this value. ## Practical Notes
Document expected ranges when sharing results.
Human perception of sound is logarithmic—doubling perceived loudness requires about 10× more intensity. Decibels match this perception and compress huge ranges (10⁻¹² to 10⁶ W/m²) into manageable numbers (0–180 dB).
Plain dB measures physical sound level. dBA applies an A-weighting filter that mimics human hearing sensitivity (less sensitive to very low and very high frequencies). dBA is used for noise regulations and exposure limits.
Two equal sources double the power. 10·log₁₀(2) ≈ 3.01 dB. So two 80 dB sources combine to about 83 dB, not 160 dB. Decibels don't add linearly—you must convert to linear power first.
Use 10·log₁₀ for power-like quantities (watts, intensity, energy). Use 20·log₁₀ for amplitude quantities (voltage, pressure, current). Since power ∝ voltage², the factor of 2 in the exponent gives the factor of 20.
85 dB is roughly equivalent to city traffic or a food blender. It's the threshold for hearing damage with prolonged exposure—OSHA limits workplace exposure to 85 dBA for 8 hours.
Yes, negative dB means the measured value is less than the reference. For example, −3 dB means half the reference power. In audio, −∞ dB represents silence (zero power).