From an analysis of new hemoglobin solution transmission spectra at various oxygen saturations $\left(S{\mathrm{O}}_2\right)$ , path lengths, and pH, we find the determination of $S{\mathrm{O}}_2$ by using the classical oximetry technique to be poorly calibrated. We used this data set to develop a proposed method for $S{\mathrm{O}}_2$ determination based on the spectral shift of the hemoglobin transmission minimum between 475 and 510 nm. The method does not require accurate knowledge of hemoglobin extinction coefficients and is linear in relation to $S{\mathrm{O}}_2$ despite changes in path length, pH, or hemoglobin concentration.