Management zones are a pillar of Precision Agriculture research.  Spatial variability is apparent in all fields, and assessing this variability through measurement devices can lead to better management decisions.  The use of Geographic Information Systems for agricultural management is common, especially with management zones.  Although many algorithms have been produced in research settings, no online software for management zone delineation exists.  This research used a common grouping technique based on minimizing the sum of squares between groups to create an open source tool called EZZone for management zone delineation.  The tool is accessible by anyone at ezzone.pythonanywhere.com, and allows users to upload their data for delineation.  The tool is designed to be user friendly and easily integrate with other GIS software.  EZZone was applied and evaluated on data collected from small to large fields, as well as fields incorporating Variable Rate Technology.  Five fields were chosen from Georgia, USA, the UK and Greece.  The zones were constructed in these fields until the Goodness of Variance fit was above 0.8.  The results for each field are discussed and the strengths and weaknesses of the algorithm are examined.