Methods, apparatus, systems, and articles of manufacture to correlate a demographic segment with a fixed device are disclosed. An example method includes accessing a record indicating a public Internet Protocol (IP) address used by a fixed device. A monitoring data record received from a mobile device is accessed. A demographic segment of a user of the mobile device is determined. The mobile device is associated with the fixed device when an IP address of the mobile device from the monitoring data record matches the public IP address used by the fixed device. The demographic segment of the user of the mobile device is associated with the fixed device based on the association of the fixed device and the mobile device.