TITLE: Calculate left and right position of 2d elements
QUESTION [0 upvotes]: I'm trying to calculate the left and right position of a grid layout. 
This is the information I have:
ContainerWidth: 960px;    
GutterWidth:20px;         (GR + GL)
NumberOfColumns:16;       (C * 16)
ColumnWidth:40px          (C)

I need to calculate their positions respective to the ContainerWidth as a percentage:
Example for one loop, I should be able to get these values:
GL: start 0%        -  end 1.04167%;
C : start 1.04167%  -  end 6.25%;
GR: start 6.25%     -  end 7.29167%

etc
so the above would be continued for the length of (NumberOfColumns)
However, I'm not even sure if the above math is correct, how could I calculate this?

REPLY [1 votes]: The total width of the columns is $16 * 40=640$ pixels.  They fill up $960-20=940$ pixels (subtracting the gutter).  There are $19$ gaps between the columns, so the width of one gap is $\frac {940-640}{19}\approx 15.789$  They don't fit evenly.  If you round up to $16$, you will have four extra pixels.  I'll do that.  The first one covers $10$ to $50$.  The second covers $66$ to $106$ etc.  If you count the columns from $0$, column $n$ covers $10+56n$ to $50+56n$.  To get percentages, you just divide, so column $1$ covers from $\frac {66}{960}= 6.875\%$ to $\frac {106}{960} \approx 11.04\%$.  I'm not sure what the percentages help, but there they are.
{"set_name": "stack_exchange", "score": 0, "question_id": 439432}