There is an actual error in the sentence. This makes it extra difficult to read. At the end of the sentence, "produkt mängd" is wrong - it should be one word: "produktmängd", or you can use the same translation as previously in the sentence, "mängd produkt". Other than that, a comma placed after "konsumeras" could make it a bit easier to read.

Förutsatt att all produkt som inhandlas
även konsumeras
är
ett optimalt förhållande mellan mängd förpackningsmaterial och mängd produkt
så lite material som möjligt per produkt mängd

Assuming that all the product bought
is also consumed,
(then)
the ideal ratio between packaging and product
is
the least possible amount of material per quantity of product

-- English moves the main verb, and I at least would add ´then´.

RIP my old Latin teacher who actually taught us to parse sentences ;-)
HTH

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Note added at 5 hrs (2010-12-02 13:01:31 GMT)
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Förutsatt att all produkt som inhandlas
även konsumeras
är
ett optimalt förhållande mellan mängd förpackningsmaterial och mängd produkt
så lite material som möjligt per produkt mängd
______________________
The Swedish sentence simply as before, but with line breaks
______________________

Assuming that all the product purchased is consumed,
(then)
the ideal ratio between packaging and product
is
the least possible amount of material per quantity of product
_______________

It does in fact make a difference whether all the product is consumed.

You can reduce the amount of packaging per quantity of product by selling very large packs of it -
ten packs weighing 100g each take more packaging than one pack weighing a kilo.

However, if the product is perishable, food for instance, then at some point large packs will mean a waste of the product, which is not optimal.