fr Relative Unit

The CSS grid relative sizing unit fr is used to split rows and/or columns into proportional distances. Each fr unit is a fraction of the grid’s overall length and width. If a fixed unit is used along with fr (like pixels for example), then the fr units will only be proportional to the distance left over.

/*
In this example, the second column take 60px of the avaiable 100px so the first and third columns split the remaining available 40px into two parts (`1fr` = 50% or 20px)
*/

.grid {
  display: grid;
  width: 100px;
  grid-template-columns: 1fr 60px 1fr;
}