OBJECTIVES: People's confidence in their ability to look after their own health has become an important outcome measure for many long term conditions and services. We set out to develop and validate a short generic measure of patient's confidence and engagement for use in evaluation of patient-centred care and quality improvement programmes.  METHODS: The Health Confidence Score (HCS) evolved through multiple iterations with two main stages, both involving surveys of the general public (n=1031 and n=378 respectively). The HCS has four items, covering people's confidence in their knowledge of their health, their ability to self-manage, to access the help they need, and participate actively in shared decision-making. Each item is has a four point response scale from strongly agree to disagree. Each of the four dimensions may be reported independently and as an aggregate summary score. RESULTS: The Health Confidence Score is short (50 words) with a low required reading age (reading age 8). Comparable measures, such as PAM are longer (293 words), with higher reading age (12). The psychometric properties of the final version are good (e.g., Cronbach’s α = 0.82 is in the desired range) and the distribution of responses is as expected. The correlation with the My Health Confidence rating scale is high (r=0.76). Testing construct validity, as expected, the summary HCS scores are positively correlated with individuals' health status measured using howRu (r=0.49), and less so, negatively, with the number of medications taken (r=-0.29) and age (r=-0.22). People with poorer health tend to be less confident in their ability to deal with it.  The HCS is not significantly associated with ethnicity, having children or education level in our sample. CONCLUSIONS: The Health Confidence Score is short, quick and easy to use, with good psychometric properties and construct validity.