Methods and apparatus to determine ratings information for online media presentations are disclosed. An example system includes a beacon server and an impression monitor server. The beacon server is to send pingback instructions to a client device. The pingback instructions cause the client device to transmit first pingback messages to the impression monitor server at intervals designated by the pingback instructions and in response to a presentation of media via the client device. The pingback instructions further cause the client device to transmit a second pingback message to the impression monitor server in response to a skip request associated with the presentation of the media via the client device. The impression monitor server is to log impressions corresponding to the first pingback messages and the second pingback message. The impression monitor server is also to determine a duration impression for the media based on the logged impressions.