Break the shape into smaller regular shapes
Find the area of each regular shape
Add the areas together
Subtract any missing parts or cutouts
Use a grid and count full and partial squares
Estimate partial squares as fractions of a square
Use coordinate geometry if the shape is on a graph
Apply the shoelace formula for polygon coordinates
Use a known reference shape for comparison
Trace the shape and measure it with graph paper
Use a formula for composite shapes when available
Measure dimensions carefully before calculating