A seat weight sensor for detecting the load upon a vehicle seat. The seat weight sensor includes a seat rail positioned under the vehicle seat. A lever arm is mounted to the vehicle seat. One end of the lever arm has one or more stationary fingers and a free finger. The stationary fingers are rigidly mounted to the seat rail. The lever arm bends in relation to the force placed upon the seat that in turn places the free finger in motion. A sensor is mounted to the seat rail and is configured to measure the change in motion of the free finger when a force is placed upon the seat.