The proportion wheel

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For every painting workshop I’ve taught since the 1980’s,  I always listed a proportion wheel as one of the items on the supply list. Ninety percent of the time students came to the workshop empty-handed  “What’s a proportion wheel?”, they would ask. I learned quickly to always have an abundant supply on hand for them to purchase.

I first used a proportion wheel as a freelance illustrator, and today, working in the fine arts, it’s still one of those indispensable tools that can be found in my studio.

What is it about this handy little aid that is so helpful to artists?

The proportional scale is a very useful tool and a significant time saver when determining if a preliminary sketch and the canvas selected for its enlargement are of the same proportion. Why is this important? Through my years of teaching I have found some students give little attention to this important detail. Typically, after creating a sketch and deciding to use it as the basis for a painting, they will go to their closet and pull out a canvas…any canvas. Often the canvas will not be proportional to their sketch, thereby nullifying the sketch. Think of it this way; if the sketch or field study is one proportion, say 4.5″ x 6″, and the canvas selected for enlargement of the sketch is a 16″ x 20″, based on the wheel below, some of the sketch will have to be left off as it will not fit on the canvas. Hence, the composition will be changed and the sketch somewhat nullified.


Click to enlarge

So let me explain how the wheel works. First of all, notice that there are two rotating disks, the smaller disk (Size of Original), and the larger disk (Reproduction Size). For the purposes of this instruction, forget the labels and just concern yourself with the numbers, 1″ – 100″, on each of the disks. The beauty of this tool is that once the applicable numbers are lined up, everything around the wheel is proportional to those numbers. Let’s use the example mentioned earlier. If your sketch/field study is 4.5″ x 6″, what size canvas should be selected in order to accommodate 100% of the sketch? The illustration of the wheel above gives the answer.

Notice on the left side of the wheel that those two numbers (4.5″ x 6″) have been aligned; see that? The beautiful thing…all sizes around the wheel are now proportional to that size…9″ x 12″, 12″ x 16″, 18″ x 24″, 30″ x 40″, and everything in between. If you begin by measuring your sketch first, aligning those numbers on the proportion wheel, and then selecting the appropriate canvas, you will never have conflicting proportions again. Conversely, if you want to use an 18″ x 24″ canvas, for example, you can also easily determine what possible sizes your sketches must be in order to make them proportional to the 18″ x 24″ canvas; examples: 2.25″ x 3″, 3″ x 4″, and so on. One word of caution, if you can’t afford custom made frames, it’s important that you begin with standard size canvases and do your preliminary sketches proportional to your canvas choice.

Another little tidbit. Don’t concern yourself with the little window labeled (Number of times of reduction). This window is for determining the percentage of reduction or enlargement for print media. For example, if a reproduction of your 18″ x 24″ painting needs to fit in a magazine column that’s 2.5″ wide, this window will tell the photographer the percentage of reduction needed to make that happen.

The images below illustrate what happens to the composition of a sketch if a canvas of a differing proportion is chosen.

This is the original sketch and the composition selected for a 30" x 40" canvas. Sketch size: 4.5" x 6" - Gray markers and felt tip pen.

This is the original sketch and the composition selected for a 30″ x 40″ canvas. Sketch size: 4.5″ x 6″ – Gray markers and felt tip pen.

Sketch has been cropped in order to be proportional to 6" x 10", 12" x 20", 18" x 30", etc.Notice some of the foreground and sky had to be removed. Felt pen and gray markers - 3.75" x 6".

Sketch has been cropped in order to be proportional to 6″ x 10″, 12″ x 20″, 18″ x 30″, etc. Notice some of the foreground and sky had to be removed. Felt pen and gray markers – 3.68″ x 6″.


Notice that when the sketch and canvas are of two different proportions, the composition will of necessity be changed; not that any of the compositions shown here would not be acceptable, but when the composition is changed, so is your original concept.

Square composition. Felt pen and gray markers - 4.5" x 4.5".

Square composition. Felt pen and gray markers – 4.5″ x 4.5″.


Sketch is now proportional to 8″ x 10″, 16″ x 20″, 24″ x 30″, etc. Felt pen and gray markers – 4.5″ x 5.68″.


I often do my sketches on what is called “Quad Paper”; it is a gridded paper containing four squares per inch. It’s very helpful in sizing one’s sketches.

Hope this explanation of the proportional scale has been helpful. If you purchase one and practice using it, it will be one purchase you’ll never regret.



John Pototschnik is an Art Renewal Center Associate Living Master
To view his art and bio, please click HERE.



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