How much weft yarn do you need? A quick guide for weavers

When planning a weaving project, most of the thinking goes into the warp — but this article is about the weft. I will show you how to calculate exactly how much weft yarn you need. And don't worry: the maths is logical, and in the end it is simpler than it first looks.

If you are looking for high-quality rigid heddle looms, floor looms or weaving yarns, take a look at our shop – Berliner Webstühle –.

Why calculate weft yarn at all?

Knowing how much yarn you need before you start saves you unpleasant surprises at the loom: running out of yarn halfway through is not just annoying, with hand-dyed yarns it can also leave a visible colour difference. And if you plan to sell your project, or you are working to a set budget, reliable planning is worth its weight in gold.

How to calculate your weft yarn in 3 steps

1. Work out the picks per centimetre

The number of weft picks per cm (in English usually given as ppi = picks per inch) is the key figure for the weft, as opposed to the ends per cm used for the warp. It depends on your weave structure, the yarn thickness and how dense you want the fabric to be.

Weave a sample and count the picks along a section of your ruler. If you are using the same yarn and a similar density as in the warp, you can also take the value from the warp.

2. Calculate the total number of picks

Multiply the planned length of your fabric in cm by the number of picks per cm. That gives you the total number of weft picks.

Here is the formula:

Woven length (in cm) × picks per cm = total number of picks

Example:

Fabric length: 160 cm

Picks per centimetre: 4 picks/cm

→ 160 × 4 = 640 picks

3. Multiply by the weaving width

Now take the planned width of your piece (measured at the reed) and multiply it by the figure from step 2.

Example:

Picks: 640

Weaving width: 26 cm

→ 640 × 26 = 16,640 cm of yarn = 166.4 m

So you need roughly 167 metres of weft yarn.

4. Convert into balls or weight

If your yarn has, say, 100 m per 50 g ball, you will need about 1.7 balls of 50 g.

Notes on yarn consumption

• A denser fabric needs more weft yarn, because you are packing more picks into every centimetre.
• Loom waste and fringes do not count towards the weft length, but you may need to weave parts twice or allow extra yarn for the edges.
• Take-up and draw-in (that is, the shrinkage during weaving and washing) should always be allowed for at 10–20 % — with wool, feel free to allow more.
• A woven sample (a mini project or "sampler") is always a good idea: it lets you test both yarn consumption and how the fabric behaves.

Conclusion: planning pays off

Yes, doing the maths before you weave may feel like a chore. But it gives you the freedom to plan your project exactly the way you imagine it. And the result? It will be something special. Something no ready-made piece of cloth from a shop can ever be: your own work.

At Berliner Webstühle we offer a wide range of high-quality looms, weaving yarns and rigid heddle looms for you to consider as you begin your weaving adventure.