MIDI Velocity Calculator
Convert a MIDI velocity value (0–127) to its equivalent level in decibels. Useful for understanding how MIDI controllers map to actual audio amplitude in samplers, synthesizers, and DAW instruments.
About this calculator
MIDI velocity is a 7-bit integer ranging from 0 to 127 that represents how hard a note is played. In audio terms, velocity maps to amplitude, and amplitude is expressed logarithmically in decibels. The conversion formula is: dB = 20 × log₁₀(velocity / 127). Dividing by 127 normalizes velocity to a 0–1 scale, where 127 equals full scale (0 dB). The factor of 20 converts the amplitude ratio to decibels (as opposed to 10 × log₁₀ used for power ratios). At maximum velocity (127), the result is 20 × log₁₀(1) = 0 dB. At velocity 64 (roughly half), the result is approximately −5.9 dB. At velocity 1, the result is approximately −42.1 dB. Velocity 0 is treated as note-off in MIDI and is mathematically undefined in this formula (log of zero is negative infinity).
How to use
Suppose a MIDI keyboard sends a note at velocity 100. Enter 100 in the MIDI Velocity field. The calculator computes: 20 × log₁₀(100 / 127) = 20 × log₁₀(0.7874) = 20 × (−0.1040) ≈ −2.08 dB. This means a velocity-100 note plays approximately 2 dB quieter than a full-force velocity-127 hit. Now try velocity 64: 20 × log₁₀(64 / 127) = 20 × log₁₀(0.5039) = 20 × (−0.2977) ≈ −5.95 dB — noticeably softer than maximum.
Frequently asked questions
How does MIDI velocity map to decibels in a sampler or synthesizer?
MIDI velocity (0–127) maps to amplitude using the formula dB = 20 × log₁₀(velocity / 127). This treats velocity 127 as 0 dBFS (full scale) and all lower velocities as progressively quieter. However, individual samplers and synths can apply their own velocity curves (linear, exponential, or custom), so the actual dB output may differ from this pure calculation. The formula gives you the theoretical linear-amplitude mapping, which is a useful baseline for understanding instrument response.
What is the dB level of MIDI velocity 64 compared to velocity 127?
Velocity 127 corresponds to 0 dB (full scale). Velocity 64 — roughly half of 127 — calculates to 20 × log₁₀(64/127) ≈ −5.95 dB. This is because the decibel scale is logarithmic: halving the amplitude (0.5 ratio) gives −6 dB, and 64/127 ≈ 0.504, very close to half. In practice this means a mezzo-forte note is about 6 dB quieter than a fortissimo note, which corresponds well to musical dynamics.
Why is MIDI velocity 0 treated as note-off instead of silence in MIDI protocol?
The MIDI specification defines a Note On message with velocity 0 as equivalent to a Note Off message. This was a design decision that allowed early MIDI devices to run-length-encode note-off events more efficiently, since a Note On with velocity 0 requires the same message type as a Note On — saving a status byte. Mathematically, velocity 0 also creates a problem: log₁₀(0) is negative infinity, meaning it has no valid dB representation. In practice, velocity 1 is the softest audible note, corresponding to approximately −42 dB relative to full scale.