How to Calculate an ADC's Voltage Step Size

An analog-to-digital converter’s actual precision — the smallest voltage change it can distinguish — depends on both its bit resolution and its reference voltage together, not bit resolution alone, and understanding this matters directly for knowing whether a specific ADC is actually precise enough for a given sensing application. A higher bit resolution sounds more precise in the abstract, but the actual voltage step size, the real-world measure of precision that matters, also depends on the reference voltage range that resolution is being applied across.

Getting the step size calculation right means understanding that the same bit resolution applied across a larger reference voltage range produces a coarser step size than the same resolution applied across a smaller range — resolution alone doesn’t tell the whole story.

What calculating ADC voltage step size actually involves

An ADC’s bit resolution determines how many discrete digital values it can represent — a 10-bit ADC has 1,024 possible values, for instance — and the voltage step size, the smallest voltage change the ADC can actually distinguish, comes from dividing the reference voltage range by that number of discrete steps. This means two ADCs with identical bit resolution but different reference voltages have genuinely different actual precision in volts, since the same number of discrete steps gets spread across a different voltage range in each case. Getting an accurate step size calculation means correctly combining bit resolution and reference voltage together, not evaluating either one in isolation, since bit resolution alone only tells you how many discrete values exist, not what voltage change each one actually represents.

This matters practically for choosing or evaluating an ADC for a specific sensing application — knowing the actual voltage step size, not just the bit resolution, is what tells you whether the ADC can actually distinguish the voltage changes your application needs to detect.

Why people get stuck here

• Bit resolution alone doesn’t tell you the actual real-world precision. A higher bit count sounds more precise, but without knowing the reference voltage it’s applied across, you don’t actually know the real voltage step size.
• The same bit resolution produces different step sizes depending on reference voltage. Two ADCs with identical resolution but different reference voltage ranges have genuinely different actual precision, which is easy to overlook if only comparing bit counts.
• Evaluating whether an ADC is precise enough for an application requires the actual step size, not just resolution. Knowing whether a sensing application’s required precision is actually met depends on the real voltage step calculation, not the bit resolution figure alone.
• Manually calculating step size from resolution and reference voltage together is an extra step people sometimes skip. Comparing ADCs by bit resolution alone is faster but skips the calculation that actually reveals real-world precision.

What a good ADC resolution calculator looks like

Combines bit resolution and reference voltage together

Correctly calculating actual voltage step size from both inputs together, rather than resolution alone, is what reveals the ADC’s real precision.

Produces a direct, comparable step size figure

Giving a concrete voltage figure makes it possible to actually compare different ADC configurations on real precision, not just bit count.

Supports evaluating whether an ADC meets a specific application’s precision needs

A clear step size calculation lets you directly check whether an ADC can actually distinguish the voltage changes your specific sensing application requires.

Common mistakes to avoid

• Comparing ADCs by bit resolution alone without calculating the actual voltage step size for their specific reference voltage.
• Assuming a higher bit resolution automatically means better real-world precision, regardless of reference voltage.
• Choosing an ADC for a sensing application based on resolution alone, without confirming the actual step size meets the application’s precision needs.
• Not recalculating step size when comparing ADCs with different reference voltage ranges, even if their bit resolutions match.

How to do it with ADC Resolution Calculator

Online Tool Store’s ADC Resolution Calculator takes your ADC’s bit resolution and reference voltage and calculates the smallest detectable voltage step, entirely in your browser.

1. Enter your ADC’s bit resolution.
2. Enter the reference voltage.
3. Get the calculated voltage step size instantly.
4. Compare against your application’s actual precision requirements.

Because it combines bit resolution and reference voltage together, you get the actual real-world voltage step size, not just an abstract bit count that doesn’t reveal true precision on its own.

Frequently asked questions

Why isn’t bit resolution alone enough to judge an ADC’s precision?

Bit resolution only tells you how many discrete digital values the ADC can represent — the actual voltage precision also depends on the reference voltage range those values are spread across, which is why two ADCs with the same resolution can have different real-world step sizes.

How does reference voltage affect the actual step size?

A larger reference voltage range spreads the same number of discrete steps across more volts, producing a coarser step size, while a smaller reference voltage range produces a finer step size for the same bit resolution.

How do I know if an ADC is precise enough for my application?

Calculate the actual voltage step size from its bit resolution and reference voltage, then compare that figure against the smallest voltage change your specific sensing application actually needs to detect.

Final thought

An ADC’s real precision comes from bit resolution and reference voltage together, not bit resolution alone. Calculate the actual voltage step size, and know for certain whether an ADC genuinely meets your application’s precision needs.

Try the free ADC Resolution Calculator