What's the trick to measuring the elastic needed for a waist band??

[MrsGrotBag]

I just know I'm being particularly dim but I can't seem to work out how you know how much unstretched elastic to use in a waistband for skirt/trousers etc for a 4 year old....

Please help

I normally cut it to the same length (width?) as their waist. Then when you sew the ends together it will stretch very slightly when they are wearing it. After all, you don't want it to be tight on them - you just want to be able to pull it on and off and not fall down easily.

what Oakmaiden said. The aim is for it not to be tight and stretched when it is around the waist, just stretched to get off down the bum and hips.

brilliant thank you both so much!
now to repair a pair of too tight trousers.....!!