Examples to determine media impressions using distributed demographic information are disclosed. An example system includes programmable circuitry to log, at a first Internet domain, a first record for a first website visit by a first client device to a website at a second Internet domain, the first record based on a hypertext transfer protocol (HTTP) request, the first record to include a timestamp, a uniform resource locator (URL), and a user identifier, the timestamp to represent a time of the first website visit, the URL corresponding to the website at the second Internet domain, and weight impression data in a report, the impression data associated with the first record and with second records, the second records corresponding to second website visits to the website via second client devices, the weighting of the impression data based on demographic distributions of audience members corresponding to the first and second records.