css3 - CSS - dynamically calculate width -

i come across width: calc(25% - 20px + 5px);

i couldn't find answer via google. wanted know how width 410px 3 boxes in each row, because right returns me 4 boxes in smaller width 410px.

any or insight appreciated.

this method resolves entire expression single value , applies element.

the thing you're trying first calculate 25% of parent element integer value , move on next operand. calculate result , apply.

i think, need lessen down parent element's width property. you'll see 3 checkboxes width of 410px.

secondly, can try make sure expression accurate while calculating result width.

try fiddle: http://jsfiddle.net/afzaal_ahmad_zeeshan/d6sq5/ see, how calc() method works.