Ask HN: What is the expected capacity for a full time developer?

At [large company] there I work as a contractor, several projects are being planned with only a limited pool of resources. Initially plans where laid expecting everyone to deliver at 100% capacity - meaning that 8 hours of work would be done during an 8 hour workday. But if you subtract lunch, meetings, procastination, interuptions et al. - what is the expected capacity (%) of an experienced developer in a semi-agile environment?