A net force, F_net = F₁ + F₂ + … (also known as a resultant force) is a vector produced when two or more forces { F₁, F₂, … } act upon a single object. on it calculated by vector addition of the force vectors acting upon the object. A net force can also be defined as the overall force acting on an object.

Figure 1: Vectors in the same direction

When force A and force B act on an object in the same direction (parallel vectors), the net force (C) is equal to A + B, in the direction that both A and B point.

Figure 2: Vectors in the opposite direction

When force A and force B act on an object in opposite directions (180 degrees between then - anti-parallel vectors), the net force (C) is equal to |A - B|, in the direction of whichever one has greater absolute value ("greater magnitude").

(Note: The illustration assumes that the object, in this case a square, has no center of mass and can be treated like a point.)

Figure 3: Parallelogram construction for adding vectors

When the angle between the forces is anything else, then the component forces must be added up using the parallelogram rule.

For example, see Figure 3. This construction has the same result as moving F₂ so its tail coincides with the head of F₁, and taking the net force as the vector joining the tail of F₁ to the head of F₂. This procedure can be repeated to add F₃ to the resultant F₁ + F₂, and so forth. Figure 4 is an example.

Figure 4: Vectors in different directions

Simply, net force is the total amount of force acting upon an object. For example: two people are pushing a box. Person one pushes with a total of 50 N. Person two pushes with 50 N as well. The total net force acting on that box is 100 N.