Bouguer Anomaly Calculator

About this calculator

Raw gravity measurements at the Earth's surface vary not just because of what's underground but because of elevation and the mass of rock sitting between the measurement point and sea level — effects that have nothing to do with subsurface geology and need to be removed before the data is useful. The Bouguer anomaly does this by applying a free-air correction (accounting for the point's height above a reference level) and a Bouguer correction (accounting for the gravitational pull of the rock slab beneath that elevation, based on an assumed crustal density) to the difference between observed and theoretical gravity.

This calculator computes that anomaly from observed gravity, theoretical gravity, elevation, and crustal density. It's a core calculation in geophysics and mineral/oil exploration, where the resulting anomaly map reveals subsurface density variations — such as ore bodies, salt domes, or basin structures — that would otherwise be masked by elevation effects alone.