How much tension to put on elastic when making briefs

I wrote a blog “how much tension to apply on elastic for bras”, and touched briefly (pun intended) on making briefs. When making a new design it can be tricky to know how much tension in the elastic to apply. I always start with approximately the same amount each time, so know after fitting whether it’s my pattern or the elastic tension needs to be tighter or looser.

I now have pen marks on my machine where to pull the elastic to when i sew so that the tension stays even, but when I first started out sewing I would measure the cut out garment then work out how much elastic I needed. I find it easier to sew this way now as I sew faster without holding onto the fiddly ends of elastics to the end of the brief waist or legs.

It all depends on the strength of the elastic for how much tension you put on the elastic. A stronger elastic needs less tension than a softer one.

If you are wondering how you can tell is you’re elastic is a strong elastic or not - hold it up to the light and stretch it. If it is a softer one then you will be able to see through it, if it is a stronger elastic you won’t. Also the stronger ones tend to be brushed back.

SO going back to how much you should pull the elastic - on a strong elastic I aim for:

And with a softer elastic I aim for: 11% on the waist and 10% on the leg.
For a stronger elastic I aim for 9% on the waist and 8% on the leg. It doesn’t sound much difference but it does make the difference of having elastic dig in and re-bound.

For example, with a softer elastic the waist of the brief below measures 34cm (on the 1/2) before applying elastic, if I reduce that by 11% then the end result will measure 30cm (on the 1/2)

Regarding if it didn’t fit, say it was too tight, you know by looking at this picture below, that you would have to add into the pattern rather than loosen the elastic, other wise the elastic would lay flat, and what you want is the waist have it going slightly upwards at the side seam like a smile.

If it laid completely flat it would be loose at the back of the brief.

Finished brief