ADC Resolution Calculator
Calculate the ideal voltage resolution of an analog-to-digital converter from its reference voltage and bit depth. Find volts, millivolts and microvolts per LSB together with total ADC levels and maximum digital code.
Total Levels = 2^N
Maximum Code = 2^N – 1
What Is ADC Resolution?
ADC resolution describes the smallest ideal voltage step that an analog-to-digital converter can distinguish according to its reference voltage and number of digital output bits.
An N-bit ADC divides its full-scale input span into 2 raised to N discrete digital levels. Increasing the bit depth increases the number of available levels and reduces the voltage represented by one least significant bit.
ADC Resolution Formula
For the ideal unipolar converter modeled by this calculator, voltage resolution is calculated as:
where Vref is the reference voltage and N is the ADC bit resolution.
The result represents the ideal voltage associated with one digital code step.
8-Bit ADC Resolution Example
Consider an 8-bit ADC operating with a 5 V reference.
N = 8
Levels = 2^8 = 256
Resolution = 5 / 256
= 0.01953125 V
This is equivalent to:
12-Bit ADC Resolution Example
A 12-bit ADC provides 4096 digital levels. With a 3.3 V reference:
= 0.0008056640625 V
= 0.8056640625 mV
= 805.6640625 µV
The smaller step allows finer ideal voltage representation than an 8-bit ADC using the same voltage range.
16-Bit ADC Resolution Example
With a 5 V reference and 16-bit resolution:
Voltage per LSB = 5 / 65,536
= 0.0000762939453125 V
≈ 76.293945 µV
ADC Resolution by Bit Depth
Using a 5 V reference, ideal ADC resolution changes substantially as bit depth increases.
| ADC Bits | Levels | Resolution at 5 V | Maximum Code |
|---|---|---|---|
| 4-bit | 16 | 312.5 mV | 15 |
| 8-bit | 256 | 19.53125 mV | 255 |
| 10-bit | 1,024 | 4.8828125 mV | 1,023 |
| 12-bit | 4,096 | 1.220703125 mV | 4,095 |
| 16-bit | 65,536 | 76.293945 µV | 65,535 |
What Does Voltage per LSB Mean?
LSB stands for least significant bit. In an ideal ADC, changing the digital output by one code represents one resolution step.
Difference: 1 LSB
If the resolution is 2 mV per LSB, then one ideal digital code step represents approximately 2 mV of input-voltage change.
ADC Levels and Bit Resolution
The number of distinct digital levels is determined only by ADC bit depth.
Examples include:
10-bit: 1,024 levels
12-bit: 4,096 levels
16-bit: 65,536 levels
24-bit: 16,777,216 levels
Maximum ADC Digital Code
Although an N-bit ADC has 2^N possible levels, counting starts from zero. The highest numerical code is therefore:
For example:
12-bit: 4095
16-bit: 65535
ADC Resolution in Millivolts
For many embedded and sensor applications, expressing resolution in millivolts per LSB is easier to interpret than volts.
For an 8-bit, 3.3 V ADC:
= 12.890625 mV per LSB
ADC Resolution in Microvolts
Higher-resolution ADCs often produce steps small enough to be more conveniently expressed in microvolts.
For a 16-bit ADC using 3.3 V:
≈ 50.354 µV per LSB
How Bit Depth Affects ADC Resolution
Adding one bit doubles the number of available digital levels. If the reference voltage stays unchanged, this halves the ideal voltage step.
9-bit → 512 levels
10-bit → 1024 levels
Higher bit depth therefore improves theoretical resolution, although real measurement performance also depends on noise and hardware accuracy.
How Reference Voltage Affects ADC Resolution
With the same number of bits, reducing the ADC reference voltage reduces the ideal voltage represented by each code step.
8-bit at 3.3 V: 12.890625 mV/LSB
A lower reference can therefore provide finer voltage steps over a smaller full-scale input range.
ADC Resolution vs ADC Accuracy
Resolution and accuracy are not the same thing. Resolution describes the theoretical spacing between digital levels, while accuracy describes how closely a real measurement corresponds to the actual analog input.
| Term | Meaning |
|---|---|
| Resolution | Smallest ideal ADC code step |
| Accuracy | How close measured value is to true value |
A high-resolution converter can still have limited real-world accuracy because of offset, gain error, reference error, noise or nonlinearity.
ADC Resolution vs Effective Number of Bits
Nominal ADC bit resolution describes the digital word width, but practical noise can reduce the amount of meaningful measurement information.
Effective Number of Bits, commonly called ENOB, is a separate performance concept that incorporates noise and distortion. This calculator uses nominal ADC bit depth only and does not calculate ENOB.
ADC Resolution vs Quantization Error
Because an ADC represents a continuous analog input using discrete digital levels, the represented voltage generally differs slightly from the original continuous input.
That difference relates to quantization error. The ADC Resolution Calculator calculates the size of one ideal step but does not calculate the error for a particular input voltage.
ADC Resolution for Microcontrollers
Microcontrollers frequently provide built-in ADCs with resolutions such as 8, 10, 12 or 16 bits. Knowing the voltage per LSB helps developers understand how register values correspond to changes in analog input.
For example, a 12-bit ADC using a 3.3 V reference has an ideal step of approximately 0.806 mV. A change of one ADC count therefore represents roughly that voltage increment under the ideal model.
ADC Resolution for Sensors
ADC resolution matters when analog sensor signals must be digitized. A temperature, pressure, current, strain, light or position sensor may produce a relatively small voltage change for a meaningful physical change.
The ADC voltage resolution indicates whether those voltage changes can theoretically correspond to different digital codes. The final physical-unit resolution also depends on the sensor’s sensitivity and signal-conditioning circuit.
ADC Resolution Calculator vs ADC Binary Code Calculator
These two pages are intentionally separate because they answer different engineering questions.
| Tool | Inputs | Primary Result |
|---|---|---|
| ADC Resolution Calculator | Vref + bit depth | Voltage per LSB |
| ADC Binary Code Calculator | Vin + Vref + bit depth | Digital binary code |
This page therefore does not ask for an analog input voltage because no individual ADC code needs to be calculated.
Ideal ADC Resolution vs Real ADC Performance
The mathematical resolution calculated here is theoretical. Real ADC performance can be affected by thermal noise, input noise, reference-voltage noise, offset error, gain error, differential nonlinearity, integral nonlinearity, clock jitter and circuit design.
A 16-bit converter therefore does not automatically guarantee that all 16 bits provide noise-free or accurate measurement information.
Important ADC Resolution Notes
ADC levels equal 2^N.
Voltage resolution equals Vref divided by 2^N.
Maximum digital code equals 2^N – 1.
The calculated resolution represents one ideal LSB step.
Increasing bit depth decreases the voltage represented by each LSB when Vref remains unchanged.
Increasing Vref increases the voltage represented by each LSB when bit depth remains unchanged.
ADC resolution is not the same as ADC accuracy.
This calculator does not calculate ENOB, SNR, quantization noise, ADC conversion code, INL, DNL, gain error or offset error.
For a real converter, use the manufacturer’s datasheet to evaluate actual accuracy and usable performance.