1. **State the problem:** We need to find the perimeter of the blue shape drawn on a 7 by 7 grid where each square side measures 1 cm. 2. **Understand the perimeter:** The perimeter is the total length around the shape. Since the shape is made of squares on a grid, the perimeter is the sum of the lengths of all outer edges. 3. **Count the edges:** Each square side is 1 cm. We count the number of edges along the outer boundary of the shape. 4. **Use the grid scale:** Each small square side is 1 cm, so counting the number of edges along the boundary directly gives the perimeter in cm. 5. **Calculate:** By carefully tracing the shape's outline and counting each edge, the total perimeter is 20 cm. **Final answer:** $$\boxed{20\text{ cm}}$$