A pressure-based piston top-dead-center ("TDC") position measurement system is disclosed, comprising: a fuel injector configured to inject fuel into a combustion chamber bounded in part by the piston; and a controller configured to control the fuel injector to cause a fuel injection when the piston is at each of a plurality of different positions relative to TDC while ensuring fuel is provided to the fuel injector at a substantially constant pressure. The controller is further configured to estimate a pressure in the combustion chamber in response to each fuel injection, fit a curve to the estimated pressures, and determine a TDC position of the piston as correlating with a maximum pressure on the curve.