Abstract Previous studies have applied Elisabeth Noelle-Neumann's Spiral of Silence Theory to social media, yet no study has used social media metrics to quantify the minority-majority opinion gap and to construct a 3D model of an actual Spiral of Silence using field data from a development discussion. This research offers five contributions: (i) an equation that measures the gap in minority-majority opinion or positive-negative social media engagement rates, (ii) a ratio which is the output of the equation, (iii) an index which is the output of the ratio and which measures the size of the spiral, (iv) a theorem that demonstrates logical transitivity of numbers to denote the presence or absence of communication, and (v) a methodology to visualize and model the shape of the spiral in 3D. This study finds that an equation modified from Facebook's engagement rate formula-one that disaggregates positive from negative engagement (minority-majority opinion gaps) and allows data to be gathered even from respondents who do not have access to Facebook-can be used to quantify and then model in 3D an actual Spiral of Silence.