Flex One: 1 CSS Class Grid System Demo

.row {flex:1}

50%
50%
33,3%
33,3%
33,3%
25%
25%
25%
25%
20%
20%
20%
20%
20%
16,66%
16,66%
16,66%
16,66%
16,66%
16,66%
12,5%
12,5%
12,5%
12,5%
12,5%
12,5%
12,5%
12,5%

This layout uses only the .row and .column class:

.column{display: flex; flex-flow: row wrap; width: 80%; margin: 0 auto}

.row{flex:1}