Gormless question re. elastic for waistbands

[Leo35]

is there a 'rule' for measuring elastic for a waistband? You know along the lines of: around your waist and add 3 cms/ 5 cms, or perhaps, deduct an amount?

I am going to replace the elastic in two pairs of pyjama trousers (both mine), and I don't want the waistband too baggy nor too tight. The PJs are lovely and soft and I don't want to replace them.

I can find online video tutorials, but I just want to know how to measure, and therefore how much to buy!

Gormless answer: I hold elastic next to skin to measure at comfortable tension, then add 1cm each side to sew together - have never heard of any rule!

Same as shodatin.

Thanks for the advice. Of course that is the most sensible approach. I think I have been over-thinking it. Apparently that is possible - oh dear...

Will go and get started tomorrow.

Agree with the above,

but would also recommend giving the elastic a shot of hot steam under the iron first, as some can shrink a bit