Ounces are units of weight but litres are units of volume. So one can't be divided into the other.
The only way they can be "standardised" is to use water which has a density of one gram per cubic centimetre. This relates weight and volume.
So we can relate ounces to grams and use the fact that 1cc=1ml=0.001 litre.
1oz=28.35g approx. This is equivalent to 28.35ml of water. 0.5l=500ml. There are 500/28.35=17.637 oz. approx.