width

<div class="box box-1">100%</div>
<div class="box box-2">480px</div>
<div class="box box-3">240px</div>

.box-1 {
  width: 100%;
  background: rgb(212, 169, 25);
}
.box-2 {
  width: 480px;
  background: rgb(14, 165, 233);
}
.box-3 {
  width: 240px;
  background: rgb(14, 165, 233);
}
.box-4 {
  width: 30rem;
  background: rgb(149, 26, 197);
}
.box-5 {
  width: 15rem;
  background: rgb(149, 26, 197);
}

.box {
  border-radius: 12px;
  color: white;
  font-family: monospace;
  font-weight: 700;
  display: flex;
  padding: 8px 16px;
  margin-bottom: 8px;
}

.wrapper {
  display: flex;
  flex-direction: column;
}