When I am planning a new project to put on the loom, after I have decided what the project will be, I need to know how much yarn I need to have for the project. There are mathematical calculations to do that will make a close estimate to how much yarn the project will need for both warp and weft. There are a lot of calculators out on the internet and in the calculations can be found in weaving books. Many weaving books will have a project planning sheet that will let you write in the numbers needed and will lead you through the calculations to do to get how much warp and how much weft the project will use.
These are all nice. I have tried several. I have a good background in math but sometimes the worksheets or written out calculations in books can be confusing. I like things nice and simple so I have taken the best of what I have seen and put together a computer Excel spreadsheet that does it all - and made this simpler than many I have seen and also uses calculations based on the weft yarn to be used that will more accurately give how much weft yarn is needed rather than a simple percentage of the warp yarn needed that is always a lower amount than warp - which I have sometimes found not always to be even close - and generally not enough weft, which means you can find yourself short. I will share that spreadsheet file with you in this article, but first you need to understand some of the numbers that it is going to ask you to enter.
First, you need to decide how long and how wide your finished project will be. This is simple enough and it is a decision that you need to make for any weaving project you want to weave. This is easiest done in inches and the spreadsheet will ask for this in inches.
ALL YELLOW cells are INPUT points - this is where you put in your numbers. ALL GREEN cells are ANSWERS! Ignore the white cells - they are there to see what is being used for calculations.
The next thing you need to decide on is what weight yarn you will be using. In knitting yarn there will be a number found on the yarn label such as #4 - which is worsted weight yarn or #3 - which is known as baby weight, sport weight, or DK weight (all the same), and others (from #1 to #7) The weight of the yarn will decide the heddle that you will use. Generally a #4 weight yarn uses an 8 or 7.5 dent heddle. You can use a thinner yarn in a heddle than the usual thickness it is made for, but you can't use a thicker yarn as it will rub and wear in the slots and holes as it passes through - if it fits through at all. A smaller thickness yarn is fine. The resulting weave will just be looser and that results in more drape in the final weaving - which can be a good thing. I am not going to go into all of the details as all of this is basic to learning how to weave. My intent here is to help and not to teach from scratch. In the spreadsheet the weight of the yarn is going to go into the epi and the ppi entries.
EPI - ends per inch and relates to WARP
PPI - picks per incn and relates to WEFT (A pick is a single passing of the shuttle from one side to the other.)
If you don't know the EPI, you can measure it easily. Take any straight ruler. Wrap the yarn evenly starting at an inch mark and wrap not too tight and not too lose to the next inch mark. Count the number of wraps and DIVIDE by TWO (2). The result is EPI.
NOW - I am going to share what I do. I decide what heddle I am going to use - let's say the 8 dent heddle that came with my Kromski loom and I know that the dent of this heddle means that it is 8 ends of yarn in one inch. Even if I am going to use a thinner WARP than the usual #4 which should come out close to 8 EPI (not always but close), the EPI I put in the spreadsheet will be 8. If I am using the same yarn for the weft, then the PPI that I put into the spreadsheet will also be 8. If you have a 7.5 dent heddle this would be 7.5 for your heddle. If I am using a thicker or thinner WEFT - I will measure this yarn on the ruler and use that number instead - why? Because this will effect the amount of weft yarn that will be needed.
When you enter the EPI you are going to get a calculated number of WARP ENDS which may be a number with a fraction. Since you can warp a fraction of a yarn, the calculator will automatically NEXT give you a whole number of warp ends - which will be HOW MANY SLOTS AND HOLES you will warp. NOW YOU KNOW HOW MANY SLOTS AND HOLES YOU WILL WARP.
Next you are going to put in the length you plan to weave - the finished length of the project. The spreadsheet is now going to calculate how much warp you need to buy. Remember all of these numbers are inches!
The spreadsheet uses a general 10% calculation for shrinkage and pull in. This is how much extra that the spreadsheet is calculating in for this. IF YOU NEED OR WANT A LARGER OR SMALLER PERCENTAGE FOR SHRINKAGE AND PULL IN, CHANGE THE % NUMBER TO WHAT YOU WANT. ALWAYS INCLUDE THE % SIGN WITH YOUR NUMBER.
YOU NOW KNOW HOW LONG EACH WARP YARN THREAD NEEDS TO BE. If you are direct warping, this is how MANY INCHES YOU NEED FOR THE REAR BEAM OF YOUR LOOM TO BE AWAY FROM YOUR WARPING PEG. (WHOLE INCHES WARP LENGTH)
At this point you get the AMOUNT OF WARP THAT YOU WILL NEED IN BOTH INCHES AND YARDS. As most yarns are labeled in YARDS, you now know how much WARP to buy.
NEXT the spreadsheet works on WEFT.
The length of your weaving has already been entered based on the above calculations and taking shrinkage into account. All you need to enter is the PPI. The amount of WEFT needed will then be calculated for you.
Understand that it is better to have more yarn than less. I always buy an extra skein of yarn more than the calculations tell me to buy. I buy in local retail stores that have no problem taking returns on yarn. If I can't return the yarn I have added to me stash for future use. Many yarns are in dye lots. This means that the yarn color when dyed may vary from one dye batch to another and those in the SAME DYE LOT will be the SAME. The yarn label will tell you the Dye Lot number or Code. Always buy the same Dye Lot number on the same color yarn that you buy for a project.
OK - Here is the link to the spreadsheet. When you go to the site the file is on, you will be able to download it to your computer. Please click on the DOWNLOAD Button on the top of the menu to the right. DO NOT USE THIS FILE ON THE SITE - EVEN THOUGH THIS IS POSSIBLE. NEVER SAVE OVER THIS FILE ON THE SITE YOU FIND IT ON. THIS SPREADSHEET IS FOR YOUR USE ONLY - DO NOT SHARE IT WITH ANYONE. IF someone wants it, send them to this article and they can download it themselves.
IF YOU DO NOT HAVE EXCEL, YOU CAN DOWNLOAD A FREE VERSION OF AN EXCEL OFFICE SUITE FROM LIBREOFFICE.
Another TIP - Put the spreadsheet file on your cell phone. There are a number of free excel compatible Android or Iphone office suite apps that will open the file and let you do calculations right in the yarn store!
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RH WEAVING CALCULATOR
