Development of an emissions inventory is frequently incorporated into many techniques and methodologies used in determining environmental impact, for example life-cycle assessment and as part of the review procedures essential to the implementation of an environmental management system. A software package has been developed for use by farmers and advisers, which seeks to encourage environmentally sound agriculture. The software acts as an informal environmental management system. An estimate of the emissions generated on-farm, coupled with performance indicators known as eco-ratings, are used to enable the setting of objectives and targets, the monitoring of progress and the success of improvement programmes. This paper seeks to describe the techniques adopted for estimating farm emissions. The development, piloting and validation of the eco-ratings have been described elsewhere. The approach used is necessarily simplistic as it relies on readily available farm data and heuristics to derive broad estimates of emissions including losses of nitrate via leaching, pesticides and gaseous losses of ammonia and methane from livestock. It is not the aim of the system to provide accurate measures of these emissions but, rather, to provide the farmer with data to identify trends which vary with farm techniques showing that as practices improve emission levels also improve. The inventory, together with the eco-ratings and text reports provided by the software give the user a variety of techniques for managing and monitoring environmental impact and improvement programmes. This paper also discusses the techniques commonly used within industry and the problems in transferring these techniques to the farm.