The weight of a structure's tuned mass damper is the total mass in kilograms or pounds of a device installed in it which stabilizes it against vibrations or sway caused by seismic, wind, or other forces. This weight includes all solid or liquid components of the damper, including water when applicable.

Water or another liquid remains part of the total when it is a component of the damping device. A value that includes only solid parts would omit part of such a device.

The device's mass is separate from the amount of movement it controls. Building sway is a distance, while the damper weight describes the installed device.