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Given the increasing environmental impacts associated with global agri-food systems, operating and developing these systems within the so-called absolute environmental boundaries has become crucial, and hence the absolute environmental sustainability concept is particularly relevant. This study introduces an approach called absolute sustainability-based life cycle assessment (ASLCA) that informs the climate impacts of an agri-food system (on any economic level) in absolute terms. First, a global carbon budget was calculated that is sufficient to limit global warming to below 2 degrees C. Next, a share of the carbon budget available to the global agri-food sector was estimated, and then it was shared between agri-food systems on multiple economic levels using four alternative methods. Third, the climate impacts of those systems were calculated using life cycle assessment methodology and were benchmarked against those carbon budget shares. This approach was used to assess a number of New Zealand agri-food systems (agri-food sector, horticulture industries and products) to investigate how these systems operated relative to their carbon budget shares. The results showed that, in 2013, the New Zealand agri-food systems were within their carbon budget shares for one of the four methods, and illustrated the scale of change required for agri-food systems to perform within their carbon budget shares. This method can potentially be extended to consider other environmental impacts with global boundaries; however, further development of the ASLCA is necessary to account for other environmental impacts whose boundaries are only meaningful when defined at a regional or local level.