ADC Resolution & Voltage Calculator
Convert ADC digital reading to voltage, calculate step size (LSB voltage), and find digital counts for 8, 10, 12, and 16-bit ADCs.
How it works
An Analog-to-Digital Converter (ADC) quantizes a continuous analog voltage into a discrete digital number. The precision depends on the ADC's bit resolution (n) and reference voltage (Vref).
Total Steps = 2ⁿ
Step Size (LSB Voltage) = Vref / 2ⁿ
Voltage = (ADC Reading / 2ⁿ) × Vref
Note: Some converters use (2ⁿ - 1) as the denominator for ratiometric scaling. Our tool uses 2ⁿ, which corresponds directly to the ideal binary quantization bin width.
Worked example
Suppose you have a 12-bit ADC (like an ESP32 or STM32) with a 3.3 V reference voltage:
- Total Quantization Steps = 2¹² = 4,096
- LSB Step Size = 3.3 V / 4,096 ≈ 0.8057 mV (805.7 μV)
- Reading 2048 (half scale) = 2,048 × 0.8057 mV = 1.650 V
- An input of 1.0 V produces: 1.0 / (3.3 / 4096) ≈ 1,241 counts
Frequently Asked Questions
What is LSB in an ADC?
LSB stands for Least Significant Bit. It represents the smallest analog voltage change the ADC can resolve, equal to Vref / 2ⁿ. For a 10-bit ADC at 5V, 1 LSB is 5 / 1024 ≈ 4.88 mV.
Why does my microcontroller ADC give non-linear readings near 0V and Vref?
Many integrated microcontrollers (such as ESP32 ADC) suffer from internal offset voltages and non-linearity (INL/DNL errors) near the ground rail and saturation rail. For high-precision measurements, use an external reference or calibrate with known voltage points.
Sources
- Analog Devices & Texas Instruments ADC architecture and quantization theory.
Results are for engineering assistance. Verify important calculations and check official datasheets. See the Engineering Disclaimer.