Pulse oximetry is a standard of care during anaesthesia in high-income countries. However, 70% of operating environments in low- and middle-income countries have no pulse oximeter. The ‘Lifebox’ oximetry project set out to bridge this gap with an inexpensive oximeter meeting CE (European Conformity) and ISO (International Organization for Standardization) standards. To date, there are no performance-specific accuracy data on this instrument. The aim of this study was to establish whether the Lifebox pulse oximeter provides clinically reliable haemoglobin oxygen saturation (SpO2) readings meeting USA Food and Drug Administration 510(k) standards. Using healthy volunteers, inspired oxygen fraction was adjusted to produce arterial haemoglobin oxygen saturation (SaO2) readings between 71% and 100% measured with a multi-wavelength oximeter. Lifebox accuracy was expressed using bias (SpO2 − SaO2), precision (SD of the bias) and the root mean square error (Arms). Simultaneous readings of SaO2 and SpO2 in 57 subjects showed a mean (SD) bias of −0.41% (2.28%) and Arms 2.31%. The Lifebox pulse oximeter meets current USA Food and Drug Administration standards for accuracy, thus representing an inexpensive solution for patient monitoring without compromising standards.