The difference between the cost price and the retail price of merchandise. Markup may be expressed in dollars or as a percent. If stated as a percent, it may be based on either cost price or retail price. Most retailers base markup on retail price.
Measure the entire shape of a curved shower rod if this is the style you have. Expect the measured width to be approximately 6 inches more than a standard curtain rod. Purchase a shower curtain with a 72-inch width, if available, to compensate for the additional width. If necessary, a 70-inch curtain width works as well. This is because the rods curve inward at the edges, making for an overall smaller width measurement.
The number of rings needed depends on the drapery. 50 wide panels will commonly use around 8 rings (7 ring spacing), but this can vary so always check your specific drapes to determine how many rings are needed. In general, you'll use a ring for every 4 - 6 inches of curtain rod.