Disclosed is a method of determining the ability to enter a parking gap starting from an initial position of a vehicle. The negotiability is determined by way of two characteristic diagrams (ymin(δ,θ,x); ymax(δ,θ,x)), with the two characteristic diagrams (ymin(δ,θ,x); ymax(δ,θ,x)) indicating for several predetermined sets of values of first vehicle quantities (δ; θ; x) a minimum value (ymin(δ,θ,x)) and a maximum value (ymax(δ,θ, x)) for a second vehicle quantity (y), and with the first vehicle quantities (δ; θ; x) and the second vehicle quantity (y) being selected from the group comprising a longitudinal (x) and a lateral (y) distance of the vehicle (1) from the parking gap (9), a yaw angle (θ) of the vehicle (1) and a steering angle (δ) at steerable wheels (2a, 2b) of the vehicle (1). A parking assist device is suitable to implement the method.