Write the vector in component form, such as v = < b1 - a1 , b2 - a2 >, where (a1, a2) and (b1, b2) are the x and y coordinates of each respective point of the vector. So, if the vector is bounded by (2,2) and (6,4), in component form, the result would be v = (4, 2).
Input the result into the equation for vector magnitude, which is v = sqrt (v1^2 + v2^2), where v1 and v2 are the respective points from the example.
Solve for the equation. Using the same example, you would compute v = sqrt (16 + 4), or the square root of 20, which is approximately 4.47. This is the magnitude.
Repeat for vectors of other directions using those vectors' distinct points.