A clamping force sensor system includes a clamping force sensor device, a signal-converting program carrier, and an output device. The clamping force sensor device includes a body mounted to a tie bar of a forming machine. The clamping force sensor device further includes a sensor mounted to the body, with a portion of the sensor exposed outside of the body. The signal-converting program carrier is electrically connected to the sensor by at least one signal line. The signal-converting program carrier includes a built-in program for converting a signal from the at least one signal line into a mold-clamping force. The output device is electrically connected to the signal-converting program carrier for outputting the mold-clamping force.