When you're figuring out the area of a shape, the units you pick are super important! Here’s how they can change your results:

1. Keep Units the Same: Always use the same type of unit for all your measurements. For example, if you have a rectangle that is 5 meters long and 3 meters wide, you find the area by multiplying. So, it’s $5 \times 3 = 15$ square meters (m²). But, if you mix up units, like using meters and centimeters, you could end up with totally different numbers!

2. Change Units When Needed: If you end up using different units, like centimeters (cm) and meters (m), make sure you change them first. For example, remember that $1$ meter equals $100$ centimeters. So, a rectangle that is 1 meter by 1 meter turns into 100 cm by 100 cm. If you calculate that area, you get $100 \times 100 = 10,000$ square centimeters (cm²).

3. See the Size of the Area: The units you choose can also change how big the area looks. Imagine a circle with a radius of 1 meter. Its area is about $3.14$ square meters. But if you measure that in centimeters, it’s around $314$ square centimeters!

So, always pay attention to your units when you calculate area. It really makes a big difference!