The Grid Method how to use the grid method to enlarge or transfer an image
In a nutshell, the grid method involves drawing a grid over your reference photo, and then drawing a grid of equal ratio on your work surface (paper, canvas, wood panel, etc). Then you draw the image on your canvas, focusing on one square at a time, until the entire image has been transferred.
To draw the grid lines on paper, I would recommend using a mechanical pencil, so that you can get a thin, precise line. Be sure to draw the grid very lightly, so that you can easily erase it when you are finished.
Let's say you want to paint the following image: This reference photo is 5" x 7". As luck would have it, you want to make a 5" x 7" painting from this photo. So drawing the grid will be pretty straightforward. But if you want to make a large painting, you could also make a painting that is 10" x 14" or 15" x 21" or 20" x 28". Why those sizes and not other sizes? Because those sizes are the same ratio as the 5" x 7" reference photo.
See? It's basic math. The size of your artwork must always be equally proportionate to the size of the reference photo.
the # of boxes on reference photo= must match/ be divisible by the inches/cm on drawing paper