Abstract: A system for measuring the tongue weight of a trailer attached to a hitching component of a vehicle is disclosed. The system includes a smart device comprising a sensor for determining the angle of the smart device with respect to horizontal and an app running on the smart device. The app is configured to take a signal from the sensor when the smart device is resting on a surface of the vehicle at a point in time when the trailer is not hitched to the vehicle and store a value “Angle Unhitched,” corresponding to the angle of the vehicle without the trailer hitched. The app is also configured to take a signal from the sensor when the smart device is resting on the surface of the vehicle at a point in time when the trailer is hitched to the vehicle and store a value “Angle Hitched,” corresponding to the angle of the vehicle without the trailer hitch attached.