For iregular surface oject such as a leaf, trace the outline of the leaf on the graph paper.
Count the number of 1 cm squares that are completely covered by the leaf.
Count the number of 1 cm squares theat are at least half covered (half or more than half) by the leaf. Add the two numbers for the total area.
If areas of the incomplete squares are less than 1/2 , than they are not counted.