When planning a weaving project, you often think about the warp – but this article will focus on the weft. I'll show you how to accurately calculate your weft yarn requirements . And don't worry: The calculation is logical – and ultimately simpler than it seems at first glance.
If you are looking for high-quality looms, looms or weaving yarns, we recommend you take a look at our site – Berliner Webstühle – to throw.
Why calculate weft yarn at all?
Knowing your yarn quantity in advance will avoid unpleasant surprises while weaving: Running out of yarn mid-weaving is not only frustrating, but can even result in visible color differences in hand-dyed yarns. And if you want to sell your project or are working within a specific budget, reliable quantity planning is worth its weight in gold.
How to calculate the weft yarn requirement in 3 steps
1. Determine weft threads per centimeter
The number of weft threads per cm (ppi for short = picks per inch) is the key measurement in contrast to the thread density of warp yarn. It depends on your weave, the yarn thickness, and the desired density.
Make a weaving sample and count the weft threads on a ruler. If you're using the same yarn and a similar density as the warp, you can also use the count from the warp.
2. Calculate the total length of the fabric
Multiply the planned fabric length in cm by the number of weft threads per cm. This gives you the total number of weft threads.
Here is the formula:
Woven length (in cm) × number of weft threads per cm = total number of weft threads
Example:
Fabric length: 160 cm
Weft threads per centimeter: 4 threads/cm
→ 160 × 4 = 640 weft threads
3. Multiply by the web width
Now take the planned width of the weaving piece (measured at the reed) and multiply it by the number from step 2.
Example:
Weft threads: 640
Weaving width: 26 cm
→ 640 × 26 = 16,640 cm yarn = 166.4 m
So you need about 167 meters of weft yarn.
4. Convert to balls or weight
For example, if your yarn has a length of 100 m per 50 g ball, you will need approximately 1.7 balls of 50 g each.
Notes on yarn consumption
- For dense fabrics, you need more weft yarn because you are working in more threads per cm.
- Warp drop and fringe do not count towards the weft yarn length, but you may need to double weave pieces or add extra yarn for the edge.
- Draw-in loss and shrinkage (i.e. shrinkage during washing or weaving) should always be taken into account at 10-20% – or even more for wool.
- A weaving sample (also called a mini-project or “sampler”) is always a good idea: you can use it to test both yarn consumption and fabric behavior.
Conclusion: Planning is worth it!
Yes, the calculations before weaving may seem tedious. But it gives you the freedom to plan your project individually – exactly as you envision it. And the result? Will be something special. Something that no finished piece of fabric from a store can ever be: your work.
We at Berlin looms offer a variety of high-quality looms, weaving yarns, and weaving frames that you can consider to begin your weaving adventure.