Open Google Maps and find your local area.

Make sure you have satellite view on.

Zoom in on your own garden and right click your mouse to bring up this menu.

Select measure distance.

A small white dot will be on the screen.

Drag the dot to the corner of your space.

Click to create a new dot in each corner of your space.

Once you have completed the shape, it will tell you the total area in a white box below.