Chamber carbon flux measurements are routinely used to assess ecosystem carbon sink/source dynamics. Often these point measurements enclose considerable vegetation biomass, with fluxes upscaled in space and time for each vegetation type. This paper assesses the importance of including the volume of peatland dwarf shrub vegetation in chamber flux calculations and outlines a simple but effective method of assessing plant volumes. It shows that inclusion of plant volumes significantly affects fluxes and that this effect becomes greater as the proportion of chamber volume occupied by plants increases. Moreover, it demonstrates that, with an initial destructive laboratory assessment for each plant species and a little practice at volume estimation, plant volumes can be accurately assessed non-destructively in the field.