how to work out how much yarn needed?

[MrsGubbins]

If I want to crochet this how do I work out how much yarn I need? I know it tells me on the pattern how much of the recommended wool but I'm not sure how to work it out if I want to use this one instead?

Can anyone explain it please! (I'm vaguely aware it's something to do with the gauge/tension....)

thank you

[moggle]

One ball of that should be enough as the pattern says 500m and the ball is 800m. Gives you plenty of leeway. If you use the same size hook it should be more or less the same amount of wool I think. I don't know of any clever way of working it out really unfortunately- maybe with knitting but crochet's a different kettle of fish.

[MrsGubbins]

oh thank you moggle.. I honestly never looked at the yardage!!