Comparing Capacity

Capacity is how much a container can hold when full. Empty means nothing is inside. Full means it holds as much as it can. Pouring water out changes the amount inside. If the container stays the same, its capacity stays the same.

A cup's shape alone does not tell you how much water is inside. Empty cups given equal amounts without spills contain equal amounts, even if their shapes differ. Bars showing water amounts do not tell you how much the cups can hold when full. For same-size cups, the fuller cup has more water.

A shaded bar can stand for how much of a container's capacity is filled. It is not a picture of the water's height. Half full means half the amount that fits. Quarter full means one of four equal amounts. Two of four make half. All shaded means full; none shaded means empty.

With an adult, use two empty containers that each fill exactly with whole small cupfuls. Use the same full small cup each time. Pour without spills and count each cupful once. More cupfuls to fill means greater capacity; equal counts mean equal capacity. If the last pour needs only part of a cupful, use the pouring test below instead.

Each pot fills exactly with these whole cupfuls. Pot D needs more, so it can hold more.

A cupful diagram has one equal space for each full small cup that fits. Count filled spaces to find cupfuls already poured. Count empty spaces to find cupfuls still needed. A quarter is one of four equal amounts. Half is half of the equal amounts.