Analog Digit / Signal tools

ADC resolution calculator

How finely does your analog input card really resolve your process? Enter the converter and the signal, and see the resolution in engineering units.

ADC resolution (bits)

ADC input min (V)

ADC input max (V)

Signal min (V)

Signal max (V)

Process value at signal min

Process value at signal max

Units

Smallest change you can see

Total counts
LSB size
Counts your signal uses
Effective resolution

How it works

An ideal ADC splits its input range into 2ⁿ steps. The size of one step, the least significant bit (LSB), is the smallest voltage change it can register.

LSB = (ADC max − ADC min) ÷ 2^bits

If your signal only covers part of the ADC's range, you only get part of the counts. A 1–5 V signal (a 4–20 mA loop across a 250 Ω resistor) on a 0–10 V input uses just 40% of the counts.

resolution = (process high − process low) ÷ counts used

Real converters lose a few bits to noise, so the effective number of bits (ENOB) on the datasheet is often 1–3 bits below the nominal figure.