Wie lange wird es Ihrer Meinung nach dauern

Hi, 

I have seen this sentence "Wie lange wird es Ihrer Meinung nach dauern" which I understand means "How long do you think it will take?". Why do we add "nach" in this sentence? Is this because the actual translation is more like "How long will it after your opinion take"?

Best,
Rex

Would it be clearer if you translated nach as "according to"?
"According to" is one of the meanings of nach in to the Leo dictionary.
So it becomes "how long will it take according to your opinion."

 So if you translate it freely it becomes "how long do you think it will take"

Hallo RexV und sfpugh, 

The word nach is a preposition. Prepositions are usually placed before the word(s) they modify and determine their case (accusative, dative or genitive).
When prepositions are placed after the word(s) they modify, they are called postpositions (which is the case in the sentence above). 
Nach always indicates the dative case.

When nach is used as a postposition it often means “according to“ as sfpugh suggested. 

The expression meiner Meinung nach can be translated to “according to my opinion“ or “in my opinion“.

Both your suggested translations to Wie lange wird es Ihrer Meinung nach dauern - “How long will it take according to your opinion“ or “How long do you think it will take“ are correct. 

If you would like to learn more about different German prepositions, have a look at lesson 20.5 “Prepositions“.

Bis bald,
Julia