# What is formula for quantization step size?

I have read from different web links,different formulas of quantization step size as shown highlighted in attached snapshot,but what is actual/correct formula?

You can find the specifics for the actual device you are using on the manufacturer datasheet, such as this example from ADI's AD9459 ADC, where the input range is from $$\pm V_{ref}$$ where $$V_{ref}$$ is an externally supplied reference voltage, and OR in the table is an out of range indicator:
That said it is sufficient in most cases to simply use the total input range (up to the backed off full scale) and divide by $$2^{b}$$ where $$b$$ is the stated precision in ENOB.
• @engr In most cases the analog input signal and the ADC itself would have noise and offsets exceeding 0.5 lsbs so yes it wouldn't make sense to determine an exact voltage threshold- just simply take the entire range and divide by $2^b$ to determine the step size in those same input units (volts for example). When you are concerned with signal fidelity and SNR, you want to be sure you are quantizing your entire signal including the noise in the signal itself, otherwise you are degrading your signal with quantization noise. – Dan Boschen Feb 25 at 6:06