12 Column grid

.row { display: flex; align-items: flex-start; }
.row:medium { display: flex; flex-direction: flex-start; align-items: center; margin: 0;}

[class*="col-"] { padding: 0 10px 0 10px; }

.col-1 {width: 8.33%;}
.col-2 {width: 16.66%;}
.col-3 {width: 25%;}
.col-4 {width: 33.33%;}
.col-5 {width: 41.66%;}
.col-6 {width: 50%;}
.col-7 {width: 58.33%;}
.col-8 {width: 66.66%;}
.col-9 {width: 75%;}
.col-10 {width: 83.33%;}
.col-11 {width: 91.66%;}
.col-12 {width: 100%;}

Equal column grids

12 columns

col-1
col-1
col-1
col-1
col-1
col-1
col-1
col-1
col-1
col-1
col-1
col-1

6 columns

col-2
col-2
col-2
col-2
col-2
col-2

4 columns

col-3
col-3
col-3
col-3

3 columns

col-4
col-4
col-4

2 columns

col-6
col-6

Unequal column grids

col-1
col-11
col-2
col-10
col-3
col-9
col-4
col-8
col-5
col-7