Consumer surplus is shown graphically as the area below the demand curve and above the market price line (and above the horizontal axis), usually forming a triangle at the top-left of the equilibrium point.

What consumer surplus means (in one picture)

  • Imagine the standard supply-and-demand graph: price on the vertical axis, quantity on the horizontal axis.
  • The downward-sloping demand curve shows the highest price consumers are willing to pay for each unit.
  • The horizontal line at the actual market price shows what they actually pay.

All the area between those two— above the price line and below the demand curve, from quantity 0 up to the quantity sold—is consumer surplus.

Why it’s drawn as an area

For a linear demand curve and a single market price, that region is a triangle, so total consumer surplus can be computed as:

Consumer Surplus=12×base×height\text{Consumer Surplus}=\tfrac{1}{2}\times \text{base}\times \text{height}Consumer Surplus=21​×base×height

where:

  • Base = equilibrium quantity (horizontal distance).
  • Height = difference between maximum willingness to pay (where demand hits the price axis) and the market price.

This is why many textbooks say:

Consumer surplus is the triangular area under the demand curve and above the market price.

Quick HTML table summary

Here’s a compact HTML table that matches the usual multiple-choice wording:

html

<table>
  <tr>
    <th>Concept</th>
    <th>Graphical description</th>
  </tr>
  <tr>
    <td>Consumer surplus</td>
    <td>Area <b>below</b> the demand curve and <b>above</b> the market price line, from zero to the quantity traded.</td>
  </tr>
</table>

TL;DR:
On a standard supply-and-demand graph, consumer surplus is the area under the demand curve and above the market price, up to the quantity actually bought and sold.

Information gathered from public forums or data available on the internet and portrayed here.