How to · Reference chart

How to stretch a canvas

The stapling order, corner folds, tools, bar depths, how much canvas to cut, and how to re-tighten a canvas that has gone slack.

By Travis Moher · Published October 28, 2026

That overage figure comes from the Fredrix stretching procedure as reprinted by Rex Art, which allows 1 1/2 to 2 in of excess for gripping and stretching, depending on the frame. Deeper gallery bars need more, because the canvas has farther to travel before it reaches the back. The table below does that arithmetic for you.

What you need

• Stretcher bars, two pairs (two of each length).
• Canvas, primed or raw, cut to size with the overage below.
• Canvas pliers. Fingers alone cannot pull even tension on anything bigger than a small panel.
• Staple gun and staples (or tacks and a tack hammer, the older method).
• Tape measure and a square, plus scissors or a utility knife.
• A rubber mallet to seat the corner joints, and keys if your bars take them.

Stretcher bar depth and how much canvas to cut

In practice: 3/4 in bars (Fredrix's standard is 11/16 in) are the studio default when the painting will go in a frame, since the frame rabbet hides the edge. Gallery bars, about 1.5 in deep from most makers and 1-3/8 in from Fredrix, are for paintings hung without a frame, with the image or a solid color wrapped around the sides and the staples hidden on the back.

Cut sizes for common frames

Sizes in the first column are stock frame sizes; our standard canvas sizes chart has the full list, and the large canvas sizes guide covers 36 in and up, where you will want cross braces.

How to stretch a canvas, step by step

1. Assemble the frame. Push the mitered corners together and seat them with a mallet, bevel side facing the canvas.
2. Square it. Measure both diagonals, corner to corner. When they match, the frame is square.
3. Cut the canvas. Lay it face down (primed side down), center the frame on it, and cut with the overage from the table. Keep the weave parallel to the bars.
4. First staple. Fold the canvas over the middle of one side and staple it to the back or the outer edge of the bar.
5. Opposite side. Turn the frame around. Grip the canvas at the middle of the opposite side with the pliers, lever it tight against the bar, and staple.
6. The other two middles. Repeat on the remaining two sides. You will see a diamond-shaped crease running between the four staples. That crease means the tension is even.
7. Work outward. From each center staple, move the pliers about 2 in along the bar, pull, and staple. Do a couple of staples on one side, then rotate and do the same on the opposite side. Keep going around the frame, center out, until you are about 2 in from each corner.
8. Fold the corners. See below.
9. Finish the back. Fold the excess canvas onto the back of the bars and staple or tape it. Do not trim it flush: Rex Art notes that a flush trim makes remounting difficult without making the frame smaller.
10. Set the keys if your bars take them, pushed in by hand, not hammered.

Tension order, and why it matters

Canvas stretches unevenly if you pull one side at a time all the way to the corners. The first side ends up tight, the last side loose, and the weave runs crooked across the face. Working center out on opposite sides means each pull is balanced by the one before it. The rule is simple: every staple you place should be answered by a staple on the opposite side before you go further.

Oil-primed linen needs more care, and the Fredrix procedure calls for closer spacing on it. Large canvases need rotating several times as you go.

How to fold canvas corners

1. Pull the corner point of the canvas straight across the back of the frame, diagonally, and staple it.
2. Fold one side flap over, making a crisp vertical fold along the corner edge, like a hospital bed corner.
3. Fold the second flap over the first so the edge lines up with the corner. Staple through the fold on the back.
4. Trim bulk inside the fold on thick canvas so the corner lies flat. Never trim the visible edge.

On a gallery wrap the corner fold is visible, so fold all four corners the same direction for a matched look.

Ready to shop

The tools and materials above. Affiliate links, so we may earn a commission at no cost to you.

Fredrix Canvas Pliers, Chrome PlatedWide jaws grip the canvas without tearing it, and the lower jaw levers against the bar so you pull with the tool, not your fingers. About $34.Check price →Arrow T50 Heavy-Duty Staple GunThe standard manual staple gun in frame shops and studios. Takes T50 staples from 1/4 to 9/16 in. About $20.Check price →Arrow 506 T50 Staples, 3/8 in, 1,250 PackA 3/8 in leg holds canvas in softwood bars without punching through the far side. About $4.Check price →Fredrix Series 123 Dixie Acrylic Primed Cotton Duck Roll, 55 in x 3 ydPrimed and ready to paint. A 55 in width covers a 24 x 36 in canvas with room to spare, or several smaller ones. About $122.Check price →Fredrix Stretcher Strip, 14 in (single)Sold one strip at a time, so buy two of each length you need. Mix lengths for any size: two 14s and two 18s make a 14 x 18. About $8 each.Check price →

Stretcher bars vs strainer bars

The difference is whether the frame can expand. The conservation wiki maintained by the American Institute for Conservation defines a strainer as a support with its corners fixed by nails or screws, dowels or splines, or glue, and a stretcher as an expandable support whose corners take keys (Stretchers and Strainers: Introduction). A strainer is cheaper and rigid. When the canvas on it goes slack, the only fix is to restretch. A stretcher lets you take up slack later by driving the keys. For anything you plan to keep, use stretchers.

Keys (wedges) and re-tightening

Keys are small wooden wedges that sit in slots inside each corner. Most stretcher frames take eight, two per corner (Wikipedia, Tightening key). Driving them deeper pushes the bars apart and tightens the canvas. To re-tighten:

• Tap each key in a small amount, then move to the next corner. Go around the whole frame evenly.
• Tap, do not pound. A key driven too hard can tear the side of the canvas.
• Check keys when you move a painting. Loose keys can fall out and damage the painting surface.
• Acrylic-primed canvas only: small ripples can be dampened on the back with a sponge and left to dry. Never wet the back of an oil-primed canvas (Rex Art).
• Large wrinkles need restretching, not keys.

Primed vs raw canvas

Rex Art's Fredrix-based instructions rank them: raw canvas is the easiest to stretch, primed cotton and Polyflax are next, primed linen is harder, and oil-primed (especially double-primed) canvas needs the most care. Raw canvas has one catch: it shrinks and tightens as you size and prime it. Stretch raw canvas firm but not drum tight, prime it, and let the primer do the final tightening.

For most painters, primed cotton duck is the place to start. Our best canvases for acrylic painting compares primed rolls and pre-stretched options if you would rather skip this job entirely.

Sources

• Rex Art, How to Stretch Artists' Canvas (Fredrix procedure). The 1 1/2 to 2 in overage, squaring by diagonals, center-out order, 2 in steps, corner folds, not trimming flush, primed vs raw ranking, and the wet-back rules.
• Fredrix Stretcher Bars and Strips, Creativation exhibitor listing. Standard 11/16 x 1-9/16 in, gallery 1-3/8 x 1-3/8 in, heavy duty 2-1/4 x 1-7/16 in.
• AIC Conservation Wiki, Stretchers and Strainers: Introduction. Definitions of strainer, stretcher, and keys.
• Wikipedia, Tightening key. Eight keys per frame, two per corner, and the cautions on over-driving and loose keys.
• Cut sizes and the gallery overage are arithmetic from the figures above.

Questions

Keep reading

• Standard canvas sizes: every stock size in one chart.
• Canvas sizes by aspect ratio: pick a shape that fits your image.
• Grid method drawing: get the image onto the canvas you just built.
• How to price artwork: what to charge once it is finished.

Written by Travis Moher for Austin Gallery, October 2026. Austin Gallery may earn a commission from product links on this page at no cost to you. See our affiliate disclosure.