A torque estimating system for an internal combustion engine includes a plurality of cylinders and estimates torque for each cylinder. A cylinder pressure of a cylinder pressure sensor (CPS) mounted cylinder #1 is acquired. Measured indicated torque Te1 resulting from an explosion in the CPS-mounted cylinder #1 is calculated based on the cylinder pressure. A first angular acceleration dω1/dt and a second angular acceleration dω2/dt are calculated. Estimated indicated torque Te2 resulting from an explosion in a CPS-less cylinder #2 is calculated using the measured indicated torque Te1 of the CPS-mounted cylinder #1 and a difference value between the second angular acceleration dω2/dt and the first angular acceleration dω1/dt.