Most weaving patterns tell you how much loom waste they allow in the warp length within the project specs. In general, I allow 18”– 22” for the direct method, which requires that you tie onto the front apron rod and 22”– 26” for the indirect, which requires that you tie onto the apron rod in front and back. How much loom waste you need for any given project depends on how much yarn you use to tie on your knots, your loom type, and your finishing technique.
Loom waste is the length of warp that you can’t weave due to loom mechanics and the bits that you use to tie onto the apron rods. I’ve observed that beginners tend to use more loom waste than more experienced weavers. This is largely due to dialing in your knotting technique. Your style of loom can also dictate your loom waste. On my Cricket, I use about 6” of loom waste in the front and 11” in the back. I increase this by 15% when weaving on my Flip. If my project includes fringe, much of this length isn’t wasted, it is used in the final project.
The next time you weave a project, take the time to do a quick loom waste audit to determine how much loom waste you actually use. If using the direct method, you can do this by measuring the amount of warp left that you can’t physically weave at the end of your project, before you cut it from the loom. Then you can cut the project free of the back apron rod, unwind the project from your front beam, untie the warp from the front apron rod, and measure how much warp you used in the front. Include your headers in these measurements. If using the direct method, you will need to untie in the front and back before taking the measurements.
By taking the time to do this, you have your own personal guideline as to how much yarn you need to allow for any given project. If you are trying out a new 
technique or fiber, I recommend increasing this amount by 10%–15%, to allow for the learning curve.
Schacht Spindle Company wrote an article in their July newsletter about lashing as a way to reduce your loom waste. It is a tried-and-true method weavers use to decrease their loom waste, particularly when they are trying to eke out those last few inches at the end of a project. I generally don’t recommend this technique for beginners because it can be tricky to get your tension even when your learning curve is steep, but after you have a few projects under your belt, you may want to experiment with lashing. That said, you never know what you can do until you try.
Heddles Up!
Liz
I’ve been busy figuring this out on a personal basis lately, so your article is timely and helpful. I have discovered that I have a definite pattern of take-in on the width (usually about 1″ less than the width in the reed) and about 4″ on the length — with an additional 14″ for fringe and the amount I can’t weave at the back-end — just as you said, I’m right at about 18″ for direct warping. Knowing this also helps on calculating yardage for the weft — I kept having a lot of leftover yarn calculating based on the total warp length. Now I calculate on the length minus fringe/waste, add on about 15%, and come a lot closer to just the right amount of yarn. Thanks, as usual, for your great tips!
Thanks for the great example of why it matters to figure out what your personal loom waste estimate. Weaving is very much a work of the hand and we all approach the work a little differenlty.
I have devised and modified my 32″ Kromski to eliminate almost all loom waste and put a layer of cloth between each layer of warp or woven work. It works so well that I am planning on adding the same system to my Louet David. I am looking for a way to make and sell the idea commercially. Any help or advise you can give would be most appreciated!
Sounds like a fun project and I don’t have any succinct words of advise, except to keep chipping away at it and the right path will open up. Start with figuring out the scope of the market and then prototyping your idea to figure out how to manufacture it. Some folks have had luck on places like Etsy where they make artisan accessories for other makers.