Geothermal Gradient Calculator

Why the Earth gets hotter with depth

Heat flowing outward from Earth's hot interior, combined with radioactive decay in crustal rocks, produces a steady temperature increase with depth known as the geothermal gradient - the basis for both geothermal energy exploitation and drilling engineering.

Worked example

For a borehole measuring 55°C at 1,500m depth, with a 15°C surface temperature:

Gradient = ((55 - 15) / 1500) x 1000 = 26.67 C per km

Setting	Typical Gradient
Stable continental crust	20 - 30 C/km
Near plate boundaries	40 - 80 C/km
Active volcanic/geothermal areas	100+ C/km

Geothermal energy developers specifically target locations with elevated gradients, since a steeper gradient means useful drilling temperatures are reached at much shallower, cheaper-to-drill depths.