SINAD ↔ ENOB Calculator
Convert between SINAD (dB), ENOB (effective bits), and THD+N for ADC/DAC characterization. The classic test-report conversion formulas.
How to Use
- Enter either SINAD (dB) or ENOB (bits); the other updates.
- Also shows equivalent THD+N and ideal quantization SNR for the bit depth.
Show Work
Formulas
History of SINAD / ENOB
The SINAD and ENOB metrics were formalized in the 1980s as sigma-delta and pipelined ADC architectures surpassed the simple flash ADCs of earlier eras. Walt Kester's ADI data-conversion handbooks (1992, 2005) codified the standard measurement procedure: apply a pure sine wave at the ADC input, FFT the output, compute signal-to-noise-plus-distortion ratio, convert via ENOB = (SINAD - 1.76)/6.02 to an effective bit depth. Today every production ADC datasheet reports SINAD and ENOB as primary specs alongside resolution.
About This Calculator
Enter either SINAD (from FFT of pure-tone ADC capture) or ENOB; the other updates via ENOB = (SINAD − 1.76) / 6.02. Also reports equivalent THD+N percentage and the theoretical ideal SINAD for the specified ADC bit depth.
Walt Kester\'s ADI "Data Conversion Handbook" (2005) is the canonical reference for ADC characterization. Everything runs client-side.
Frequently Asked Questions
What is SINAD?
Signal-to-Noise-And-Distortion ratio: ratio of signal power to total noise + harmonic distortion power, in dB. Measured from FFT of an ADC capturing a pure sine wave.
ENOB?
Effective Number Of Bits: SINAD converted back to bit-depth equivalent, via 6.02·ENOB + 1.76 = SINAD. A 16-bit ADC with SINAD = 90 dB has ENOB = 14.7 bits — 1.3 bits are lost to real-world noise.
THD+N vs SINAD?
Same thing, different sign. THD+N in dBc (down from signal) = -SINAD. For a 90 dB SINAD signal, THD+N = -90 dBc = 0.003%.
Common Use Cases
Audio ADC
AK5574 audio ADC: 114 dB SINAD, 18.6 ENOB from 24-bit output.
Oscilloscope
1 GS/s, 8-bit: 44 dB SINAD, 7.0 ENOB at low frequencies.
RF ADC
ADC for SDR: 75 dB SFDR → ~72 dB SINAD → ~11.7 ENOB at Nyquist.
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