Satellite-derived gravity models have been used in modelling of several subduction zones, but not yet for the Sumatra subduction zone. There, gravity models can shed light on the geometry and density of the plate, and whether a slab tear is present under northern Sumatra, as seismic and tomographic studies present contradicting conclusions. Ten different gravity sensitivity tests were carried out. Those tests investigated the sensitivities of the radial gravity (gR) and the second gravity gradient tensor invariant (I1) to different slab parameters (depth, thickness, density), three isostatic scenarios, and the inclusion of subduction-specific characteristics, e.g. a slab tear, and subducting crust. An innovative approach was implemented to determine slab thickness estimates based on oceanic lithospheric age, subduction direction, and a weighted half-space cooling model. Thereafter, a numerical model for the Sumatra subduction zone was developed which approximates the XGM2016 satellite-terrestrial gravity observations and supports a slab tear. The gravity sensitivity test results together with the numerical model for the Sumatra subduction zone provide a valuable and universal foundation for future gravity-based subduction zone research.