Distance Between Parallel Planes

The distance from an arbitrary point of one of the parallel planes to the other plane is called the distance between parallel planes. The point is chosen arbitrarily since all points of one plane are equidistant from the other plane if both planes are parallel.

Example: Find the distance between planes x+2y-3z+9=0 and 2x+4y-6z+1=0.
Solution: Check if the planes are parallel, for this multiply the equation of the first plane by 2 to bring them to a form where the coefficients at x,y,z are equal. 2x+4y-6z+18=0
Enter the obtained data into the online calculator, get the answer: The distance between parallel planes is 2.27172056.