# Calculating warp yarn quantity

Once you have decided on a project you may want to work out how much yarn you are going to need. This may be so you can buy or dye the correct amount without vastly over or under estimating.

The following will take you through the calculation to do this. It looks like a lot but they should be relatively straight forward things to work out. For the sake of simplicity I will work in centimetres/meters but the same can be applied to inches/yards.

The calculaion is as follows:

Total number of ends x total length of warp (m) = amount of yarn needed (m)

How to work out the total number of ends

• EPC (see calculating sett) x (width of woven piece (cm) + shrinkage/take-up (cm)) = Total number of ends
• The shrinkage/take-up is usually assumed to be 10% of the width of the woven piece but this can vary by a large amount depending on the yarn, structure and finishing. Sampling will give you a more accurate number.

How to work out the total length of the warp

• Length of woven piece(s) (m)+ shrinkage/take-up (m) + yarn wastage (m) = Total length of warp (m)
• If weaving more than one piece add the lengths together
• The shrinkage/take-up is usually assumed to be 10% of the length of the woven piece but this can vary by a large amount depending on the yarn, structure and finishing. Sampling will give you a more accurate number.
• Yarn wastage is the amount of yarn used to tie on to the front beam plus the warp woven for even end distribution plus the loom waste (the amount of yarn left on the loom not able to be woven).
• It is often easier to work out the calculations in cm and then convert to m by dividing by 100 at the end.

As a working example:

Total number of ends:

• 8 EPC
• 50cm wide warp
• 10% of 50cm = 5cm shrinkage/take-up

8 x (50 + 5) = 440 ends

Total length of warp:

• Three 50cm woven pieces = 150cm
• 10% of 150 = 15cm shinkage/take-up
• 10cm to tie on
• 5cm to weave distributing picks
• 50cm left on the loom that cant be woven

150 + 15 + 10 + 5 + 50 = 228cm (2.28m)

440 x 2.28 = 1003.2m of yarn needed for the warp