ADC Value to Voltage Calculator
Convert an ADC reading, such as Arduino analogRead(), into volts, or see what reading a voltage will give.
Formula
V = code × Vref / 2^N. A 10-bit ADC with a 5 V reference has steps (1 LSB) of about 4.88 mV. Signals larger than the reference must be scaled down first, for example with a voltage divider.
Frequently asked questions
Should I divide by 1023 or 1024?
Most ADC datasheets define 1 LSB as Vref / 2^N, which is 1024 for a 10-bit ADC. Many Arduino examples divide by 1023. The difference is at most one step (about 5 mV at 5 V), smaller than the ADC's own error.
How do I measure a voltage higher than Vref?
Scale it down with a voltage divider so the highest input stays below Vref, then multiply the reading back up by the divider ratio.