Linearity correction is performed by determining whether a data output value (DOUT) from an analog-to-digital converter (ADC) is in a first subrange or a second subrange. If DOUT is in the first subrange, then DOUT is scaled by a first scaling correction factor (SCF1), and the result is adjusted by a first best fit adjustment value (BFAV1). If DOUT is in the second subrange, then DOUT is scaled by a second scaling correction factor (SCF2), and the result is adjusted by a second best fit adjustment value (BFAV2). The data output range of an ADC can be processed in many ranges of such subranges. Techniques are set forth for determining SCF1, SCF2, BFAV1 and BFAV2. Employing the linearity correction method allows a low-cost microcontroller having an ADC to perform adequate linearity correction on the ADC output data without having to store an INL lookup table.