You are standing there, looking at the 88-inch drapery, you have brackets in hand, but how do you know where to put the bracket on the wall? Is there some formula somewhere?
Nope… but here’s how to calculate it.

Where the brackets go depends on the measurement from the top of the drape ( TOD) to the top of the drapery pin, TOP, (Measurement B in the image) how the pin attaches to the rod, (is it through a small eye screw on a ring, or through a carrier in a channel?) and the distance from the top of the drapery pin to the bottom of the bracket (BOB). (Measurement A in the image.)

I had my favorites. So I saved time by knowing the top of pin to bottom of bracket measures for all my favorites. I could then tell the installer, for example, ” on this rod,  with the 88- inch drapery, the bottom of the bracket is at 85 inches from the floor. 

I believe it’s up to the whoever specs the rod  to provide this info to the installer.

So.. to simplify things, I actually made myself a sample board of the most common brackets, attachment carriers, and rods. I used small 1-foot off-cuts  of the rods, your hardware supplier may give these to you. I used a piece of plywood I had in the workroom, it was about 24 x 16. You can use almost anything, as long as it will accommodate the bracket and rod.

So, when I had the board built, I could measure exactly the distances which are necessary. If I used a new rod, I brought it into the office and hung the brackets on the sample board, held a piece of rod in place and measured.

Let’s pretend we have a channel rod, the drapery attaches by a pin through a carrier on the rod, as in the image. Put the test rod together, place the attachment board up against a wall, resting on a table, and measure from the various points to the tabletop.

In these images there is a curtain on the rod, but it doesn’t change the calculations at all. 

Measure from the place where the pin goes through the carrier to the table.

(Measurement C).                                     7 1/2

Measure from the bottom of the bracket to the table 

(Measurement D).                                                     5 1/2

subtract  the two                                                         2      

This equals the distance between the bottom of the bracket and the top of the drapery pin.

(The PIN DROP is the distance from the top of the drape (TOD) to the top of the pin when it’s in place (TOP). In the image, that is measurement B. When you are talking to a workroom, they will ask you for the pin drop so they know where to place the pin in the pleat.)

So, recap: the measure from the bottom of the drape to the top of the pin is 7 1/2  inches,

and the bottom of the bracket is 5 1/2  inches from the floor.

Therefore the bottom of the bracket sits 2 inches below the top of the pin.

So, if the drapery is 88 inches long, and the pin drop is 1 inch. The TOP is at 87 inches from the floor and the bottom of the bracket is 85 inches from the floor.
If you want your drapery to be 1/4 inch above the floor, the BOB must therefore be 85 1/4 inches from the floor.

Another way to get these measures is to trace the silhouette of the bracket, rod and carriers and measure accordingly. 

Some drapery hardware companies supply to-scale drawings. But that’s rare.

So,, bottom of bracket to the eye of the ring… same calculations
        or bottom of the bracket to the center of the ripplefold tape

         snap  (or to the bottom of the ripplefold rod less 1/4 inch).

Here’s an ebook with bracket placement and finished length explained further. Just click the book to download.