Whether you're re-wrapping an existing cat scratching post or making a new one, if you're using rope, you'll want to know what and how much to buy.
How much rope you need to wrap a cat scratching post can be determined by how thick the rope is (e.g., 1/4", 3/8"), the circumference of the post (how much rope it takes for one wrap), and the height of the post you need wrapped (how many wraps you'll need to make).
While you can do the math yourself, I've made it easier by creating a calculator where you just put in the three measurements.
The type of rope you typically see on scratching posts is twisted sisal rope. It's generally sold in 100 foot rolls. You just need to know how many rolls to buy so you have enough but not more than you need.
The thinner the rope the easier it is to work with and fasten to the post. The thicker the rope the more durable and the less you need.
If you're simply re-wrapping a post then it's probably easiest to just measure the thickness of the existing rope and buy more of the same. If you're making a new post then consider ease of wrap (thinner) versus durability (thicker).
If what you're wrapping has the same circumference from top to bottom (i.e., it isn't wider at certain places than others) then each wrap will take the same amount of rope. To measure one wrap (if you don't have a flexible tape made specifically for this sort of thing) simply use a piece of string or rope and a measuring tape or ruler.
If your post is more oddly shaped then measure a place that seems to offer an average circumference (e.g., for a cone shaped post measure a point in the middle).
Now that you know how thick each wrap is (how thick the rope is you'll be using) and how much rope is used in one wrap (the circumference), you'll need to determine how many wraps you'll be making. Do this by simply measuring the height of the post where you'll be wrapping it (there may be a part of the post that will not be wrapped so be sure not to include that in your measurement).
To use the rope length calculator below simply enter the height of the object to be wrapped, the average circumference of the object, select the thickness of the rope you'll be using to wrap it then click on the Calculate Rope Length button.
If you forget to enter any of the info you'll get a "0" result. If this happens then just fill in any missing info and click the Calculate Rope Length button again.
Here's how much rope you'll need in feet:
You'll very likely end up with extra rope because it generally comes in 100 foot rolls (you may be able to find a 50 foot roll though it will likely cost you more per foot). Just make sure the total number of feet you buy will cover the calculated number of feet you'll need.
If you'd like to use less rope then just plan for how to reduce the scratchable area on your post or use some other material for some of that area (e.g., carpet on the bottom half with sisal rope on the top half).