Calculate the decibel difference between two power levels.
The decibel is a logarithmic unit comparing two power levels: dB = 10 × log₁₀(P1 ÷ P2). Because it's logarithmic, decibels compress a huge range of real-world power ratios into manageable numbers.
A 3dB increase roughly doubles power; a 10dB increase means 10 times the power — this non-linear scale is why decibels can feel unintuitive at first.
This power-ratio form is standard for comparing signal strengths, amplifier gain, and power levels in electronics and acoustics — a separate amplitude-based formula (using 20× instead of 10×) applies when comparing voltage or sound pressure directly rather than power.
Comparing 2W to a 1W reference: 10 × log₁₀(2) ≈ 3.01 dB — the well-known 'doubling equals about 3dB' benchmark.
The 10× form applies to power ratios; the 20× form applies to amplitude ratios like voltage or sound pressure, since power is proportional to amplitude squared — the extra factor of 2 accounts for that relationship.
Yes — if the measured power is lower than the reference, the ratio is less than 1, and log₁₀ of a number under 1 is negative, indicating a power decrease rather than increase.
No — dB is always a ratio between two values. A dB figure alone is meaningless without knowing what it's being compared against, whether stated explicitly or implied by convention.