How to Enlarge a Drawing with a Grid

I recently answered a reader comment on a post about using the grid method to create line drawings. The reader specifically wanted to know how to enlarge a drawing with a grid.

I answered the comment with basic information, but quickly realized that a post was needed.

So here we are.

How to Enlarge a Drawing with a Grid

Step 1: How Big is the Reference Photo

Here’s a reference photo for example. I actually did a drawing based on this image, and I used a grid to create the line drawing.

The reference photo is 8 x 10 inches, which I’ve found is a good size for printed reference photos. It’s large enough to show good detail, but small enough to take along if I happen to be working away from the studio.

Step 2: How Big will the Drawing Be?

When I drew this horse, I made the drawing the same size as the reference photo. That meant the drawing grid was the same size as the grid on the reference photo. That won’t help us here, so let’s say I want to make a drawing that’s 16 x 20 inches.

Step 3: How Much Bigger is the Drawing than the Reference Photo?

Using the two numbers above (8 x 10 and 16 x 20,) we can see that the line drawing will be twice as tall and twice as wide as the reference photo. That means that the grid I make for the line drawing needs to be twice as big as the grid I draw on the reference photo.

So what does that look like?

Step 4: How Much Bigger is the Drawing Grid than the Reference Photo Grid?

Here’s the reference photo with the grid on it. Let’s say that each of the lines is one inch apart (I don’t remember for sure how far apart they are, so we’ll use a nice, round number!)

TIP: I numbered the squares here and on my line drawing grid. I started numbering grids with large pieces so it was easier to use the grid. Numbering the squares meant I didn’t have to constantly count boxes when drawing! You don’t have to number your grid.

Below is the grid for the line drawing. I chose an image that shows the first stage of the drawing so you could see what I did.

Remember, I said the line drawing was the same size as the reference photo? That means that each square on the line drawing grid (below) was the same size as the squares on the reference photo (above.)

In other words, I made the drawing grid with 1-inch squares; the same as the reference photo grid.

But we want to make a line drawing that’s twice as big. To do that, the squares on the line drawing grid need to be twice as big as the squares on the reference photo.

Since the lines on the reference photo grid are 1 inch apart, the lines on the drawing grid need to be 2 inches apart.

But What About Other Sizes?

This method works no matter how much bigger you want your drawing to be.

If I wanted the drawing to be 12 x 15 (1-1/2 times larger than the reference photo,) I would draw the drawing grid with lines are at 1-1/2 inches apart.

If I wanted the line drawing smaller than the reference photo, I can do that, too. A 4 x 5 inch drawing is half the size of the 8 x 10 reference photo, so I’d make a drawing grid with lines that are half an inch apart.

What if the Reference Photo and Drawing Are Different Shapes?

The reader who asked the original question needed to enlarge a 4 x 6 photo to a 9 x 12 or 11 x 14 drawing.

Neither one of those drawing sizes are are the same shape as the reference photo. If she just doubles the reference photo, she’ll end up with a drawing that’s 8 x 12.

If she enlarges the reference photo 2-1/4 times, she’ll have a drawing that’s 9 x 13-1/2 inches.

What should she do?

Adjust the Reference Photo First

Whenever I have this problem, the first thing I do is adjust the reference photo.

Here’s a photo from my list of potential projects. It’s 10 inches wide by 7.158 inches tall. Not a standard size!

If the final portrait is to be 10 inches by 8 inches, then all I need to do is make the photo 8 inches tall, then trim a little bit off one side or the other

So that’s what I did. Not only is the reference photo now the same shape as the proposed drawing, but it’s a better composition.

Now I can double the size of the grid, just like I did in the steps above.

Adjust the Drawing Size

The nice thing about colored pencils is that we use them on paper most of the time. If you buy full sheets of paper, then you can make your drawing any shape you want within the limitations of that sheet of paper.

For example, let’s say I want my cat portrait to be the same shape and composition as the original reference photo, but twice as big. All I need to do is put a grid on the reference photo, then make the drawing grid twice as big. The resulting drawing will be roughly 20 inches wide and 14 inches tall.

One Final Note

Both of the photos in this article are digital photos. It was quite easy to crop them using a photo editor. I used Affinity Photo, but you can crop a photo in any good photo editor.

The reader who asked the question gave me the impression she had a print photo. In that case, you can do some basic cropping by first scanning it into digital form. If you have a printer/scanner or a standalone scanner handy, you can scan your own photos.

If you don’t have a scanner, most office supply shops can scan your photo for just a few dollars.

That’s How to Enlarge a Drawing with a Grid

There is one important thing to remember with using drawing grids. The reference photo grid and the drawing grid MUST be the same proportions. If they are different, your line drawing will be distorted.

If you’re interested in seeing how I made the first drawing in this post, you can read the step-by-step here.

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