1kg box = 160 pieces per box
160 pieces makes 30-32 bomboniere with 5 pieces in each
If you need to do 180 bomboniere you would do the following to work out how many kilos you need exactly.
180 (bomboniere) x 5 (pieces of confetti) = 900 (pieces total)
900 / 160 (the amount in each box) = 5.625 boxes
Round this off to the next whole number, which is 6.
You now know you will need 6 boxes to complete your bomboniere.