Steps of Deriving the consumption curve from saving curve :
(i) Draw ${45}^{\circ }$ line from the origin.
(ii) Take OC equal to OS on Y-axis
(iii) Draw perpendicular line form $\mathit{B}$ to $\mathit{R}$ on $\mathit{O}\mathit{X}$ axis which intersect ${45}^{\circ }$ line at point $\mathit{B}$.
(iv) Join $\mathrm{C}$ and $\mathrm{B}$ and extend it to get consumption curve $\mathrm{CC}$ .
In the given figure, a straight line saving curve is plotted showing saving function at different levels of income. It shows negative saving at zero level of income and zero saving level at OR level of income. At point $\mathrm{R}$, consumption expenditure = income, whereas to the left of $\mathit{R}$, consumption expenditure is less than income.
At zero level of income, consumption expenditure is shown as $\mathit{O}\mathit{C}$ which is equal to dissaving of $\mathit{O}\mathit{S},\mathit{O}\mathit{C}=\mathit{O}\mathit{S}$. Thus $\mathit{C}$ is the starting point of consumption curve. At OR level of income, saving is zero, it shows that consumption expenditure must be equal to income of $\mathit{O}\mathit{R}$. This enables to plot $\mathit{O}\mathit{D}$ as consumption expenditure equal to $\mathit{O}\mathit{R}$, which in turn gives a point $\mathit{B}$ on 45 degree line showing $\mathit{O}\mathit{D}$ equal to OR. Thus B becomes the point on proposed consumption curve.
$\mathit{B}$ is the point on consumption curve at which total consumption expenditure $\left(\mathit{C}\right)$ is equal to income (Y). At point B, APC $\left(\mathit{C}∕\mathit{Y}\right)=1$.