Abstract The forces on a single Bose–Einstein condensate confined between two parallel plates consist of two components, namely, surface tension force and Casimir force. In canonical ensemble, these forces are quite different from the one in grand canonical ensemble. In small region with distance
ℓ between two parallel plates, using double parabola approximation, we find that surface tension force decreases as
ℓ−3, whereas the Casimir force, in one-loop approximation of the quantum field, is proportional to
ℓ−13/2. The total force is also considered and its veer is found.