Buoyant force is equal to the weight of the total amount of liquid displaced by an object when submerged partially or completely in the fluid. This means that if an object that has a volume of 2m³ has 50% (1m³) of its volume submerged in water, the buoyant force will be equal to the weight of 1 m³ of water, this is about 1000kg.
With this in mind, the buoyant force will be equal to the weight of the amount of fluid that has the same total volume as the object when the object is completely submerged, this is to say, it has its total volume under the fluid.