Use the distance formula between two points: (d=sqrt{(x_2-x_1)^2+(y_2-y_1)^2})
For 3D points, use: (d=sqrt{(x_2-x_1)^2+(y_2-y_1)^2+(z_2-z_1)^2})
Subtract the coordinates of the two points
Square each difference
Add the squared values
Take the square root of the sum
For speed and time, use: (d=v times t)
For constant acceleration, use: (d=vt+frac{1}{2}at^2)
For motion with initial velocity, use: (d=ut+frac{1}{2}at^2)
For a map or scale drawing, use: (text{actual distance}=text{map distance} times text{scale})
For curved paths, use the path length or arc length formula
Convert all units to the same unit before calculating
Check the result using the correct unit of distance