How to · Reference chart

Grid method drawing

How to scale any photo or sketch onto paper or canvas with a grid: the steps, a grid size chart for common sizes, the diagonal variant, and how to get the lines back out in every medium.

By Travis Moher · Published October 28, 2026

The method is old. The Getty Museum calls it squaring: both surfaces are ruled off into an equal number of squares, and the lines inside each square are transferred freehand to the matching square on the new surface (Getty glossary). Studios used it to move small drawings onto big canvases and walls long before projectors existed. It still works for the same reason: a whole face is hard to copy, but one square holding a corner of an eye and part of a brow is easy.

Grid method step by step

1. Match the shapes. Your reference and canvas need the same aspect ratio. Divide each side of the canvas by the matching side of the reference. If both answers match, you are set. If not, crop the reference to the canvas shape first (see the worked example below).
2. Pick a square size for the reference. Choose a size that divides both sides evenly. On a 4 x 6 in photo, 1 in squares give a 4 x 6 grid. Use 1/2 in squares for a detailed portrait.
3. Grid the reference. Work on a print or a photocopy, never the original. Rule the lines in pen. A clear graph ruler keeps them square to the edge.
4. Grid the canvas. Multiply the reference square by the scale factor. At 4x, 1 in becomes 4 in. Mark every 4 in along all four edges, then join the marks. Use a light HB or 2H line.
5. Label both grids. Letters across the top, numbers down the side, on both. A1 on the photo is A1 on the canvas. This one step prevents most copying mistakes.
6. Copy one square at a time. Note where each line enters and leaves the square edge, as a fraction of the side (a third down, halfway across). Place those points, then join them. Cover the rest of the photo with paper if the full image distracts you.
7. Check the big shapes. Step back after every few squares. A proportional divider set to your scale factor checks any measurement in seconds.
8. Remove the grid. Erase or cover the lines, depending on your medium (table below).

Grid size chart

These pairs share the same aspect ratio, so the grid divides evenly with no crop. Every value is arithmetic: scale factor = canvas side / reference side, and canvas square = reference square x scale factor.

Need a canvas that matches your photo? Our standard canvas sizes chart lists every stock size, and the canvas aspect ratio guide groups them by shape so you can find one that fits a 2:3 or 4:5 photo without cropping.

Scaling math with a worked example

When the shapes match

Photo: 4 x 6 in. Canvas: 16 x 24 in. Short sides: 16 / 4 = 4. Long sides: 24 / 6 = 4. Both are 4, so the scale is 4x. Grid the photo in 1 in squares (4 across, 6 down). Grid the canvas in 4 in squares (4 across, 6 down). Same 24 squares, four times bigger.

When the shapes do not match

Photo: 4 x 6 in (2:3). Canvas: 16 x 20 in (4:5). Short sides: 16 / 4 = 4. Long sides: 20 / 6 = 3.33. The numbers differ, so a straight grid would stretch the image. Use the smaller factor or crop. Cropping is usually better: trim the photo to 4 x 5 in (cut 1 in off the long side), and now 16 / 4 = 4 and 20 / 5 = 4. Grid the cropped photo in 1 in squares and the canvas in 4 in squares.

Squares that do not divide evenly

Sometimes the canvas square comes out awkward, like 2.67 in. Work backward from the canvas instead. Pick an easy canvas square (3 in), count how many fit (a 24 in side holds 8), then divide the reference side by the same count (6 in / 8 = 3/4 in). Both grids have 8 squares on that side, which is all that matters.

The diagonal grid method

A diagonal grid adds lines from corner to corner through each square, so every square becomes four triangles. You get more reference points without making the squares smaller, which matters on curves, eyes, hands, and anything set at an angle. Two common versions:

• Square plus diagonals. Draw the normal grid, then add an X through only the busy squares. Less to erase than diagonals everywhere.
• Diagonals only. Skip the square grid and rule diagonal lines in both directions, making a diamond lattice. Some artists find the diamonds less likely to make them draw blocky, square-shaped forms.

The math does not change. Diagonals connect the same corners on both grids, so they scale automatically.

How to erase grid lines by medium

Two notes behind the table. On fixative under oil, John Bickford of The Artist's Magazine advises a light spray only, since oil paint needs to bond with the ground and a heavy coat can seal it (Painting Over a Fixative). On transfer paper, Saral's wax-free sheets leave no wax residue, so the line erases like pencil (product description). Waxy carbon-style papers do not erase cleanly and can resist paint.

What you need

A pencil and a straight edge are enough to start. These make it faster and cleaner. Affiliate links, so we may earn a commission at no cost to you.

Westcott B-85 18 in 8ths Graph Beveled RulerA clear ruler with a printed graph lets you square every line to the edge without a T-square. 18 in reaches across most canvases up to 18 x 24. About $11.Check price →Accurasee Artist 11 Inch Proportional DividerSet it to your scale factor and it transfers any single measurement from photo to canvas. The fast way to check a square without counting. About $10.Check price →Saral Wax-Free Graphite Transfer Paper, 12 1/2 in x 12 ft RollFor the final step: draw at full size on paper, then transfer it to canvas. Wax-free, so lines erase like pencil. About $19.Check price →Prismacolor Premier Kneaded Rubber Eraser, MediumLifts grid lines off paper without scuffing the surface. Press and roll; do not scrub. About $5.Check price →

Grid method vs projector vs light box vs transfer paper

Many artists combine them: grid a full-size drawing on paper, then move it to canvas with transfer paper so the canvas never sees a grid line. For murals and very large work, a projector saves hours; see our best art projectors for tracing. For paper-to-paper tracing, a light box is the cleanest option. And if you work digitally, every drawing app can lay a grid on its own layer; our drawing tablet guide covers the hardware.

Common grid method mistakes

• Mismatched shapes. A 2:3 photo on a 4:5 canvas stretches everything. Crop first.
• Unlabeled grids. Losing your place by one square shifts a whole feature. Label rows and columns on both.
• Heavy canvas lines. A grid you can see from across the room is a grid you will fight under thin paint.
• Copying objects instead of lines. Draw what crosses the square, not the nose you know is there.
• Gridding the original. Always work on a print or copy of the reference.

Sources

• J. Paul Getty Museum, Glossary: Squaring. Definition of the method: equal squares on both surfaces, lines copied freehand square by square.
• John Bickford, “Painting Over a Fixative,” The Artist's Magazine. Light fixative spray only under oil, since a heavy coat can seal the ground.
• Saral Wax Free Transfer Paper, product description (eQuilter). No wax residue, erases like pencil, works on canvas and paper.
• Grid sizes and scale factors on this page are arithmetic (canvas side / reference side), not quoted from a third party.

Questions

Keep reading

• Standard canvas sizes: every stock size in inches and centimeters.
• Canvas sizes by aspect ratio: match a canvas to your photo.
• How to stretch a canvas: build the surface before you grid it.
• Best art projectors for tracing: the fast route for murals.

Written by Travis Moher for Austin Gallery, October 2026. Grid sizes are calculated, not measured. Austin Gallery may earn a commission from product links on this page at no cost to you. See our affiliate disclosure.