Reference · Size guide

1/8, 1/4, 1/2 and Full Sheet Canvas and Paper Sizes in Inches and cm

The fraction sizes on watercolor pads, blocks and canvas boards all come from one sheet: the 22 x 30 inch imperial. Here is every fraction in inches, centimeters and millimeters, the nearest A-series size, and the pads, blocks and boards that actually match each one.

By the Austin Gallery editors · September 8, 2026

Where the fraction sizes come from

Watercolor paper has been made in a sheet called the imperial for a long time, and the imperial is 22 x 30 inches. Mills still make it: Arches, Fabriano Artistico, Saunders Waterford and Strathmore all sell loose watercolor paper as a 22 x 30 sheet, often labeled 56 x 76 cm on metric packaging. Because painters rarely work at the full size, the sheet gets torn or cut down, and the pieces are named by the fraction of the full sheet they represent.

The cut is always across the long side. Cut a 22 x 30 sheet once and you get two 15 x 22 half sheets. Cut a half sheet across its long side and you get two 11 x 15 quarter sheets. Cut again and you have 7.5 x 11 eighth sheets. The system is why an 11 x 15 pad is the single most common watercolor pad size in the world: it is a quarter sheet, and four of them tile a full sheet with nothing wasted.

The same names spread to canvas. In India, the UK, Australia and much of Asia, canvas boards and small stretched canvases are sold as 1/8, 1/4 and 1/2 sizes, and searches like "1/8 canvas size in cm" almost always mean this system. The dimensions are the same as the paper fractions, though some board makers round to the nearest inch, so a "1/4 canvas" can arrive as 11 x 14 or 12 x 16 instead of 11 x 15. Read the listing.

Fraction sheet sizes in inches, cm and mm

All conversions use 1 inch = 2.54 cm exactly. The A-series column shows the ISO 216 size closest to each fraction; in every case the A size is a little larger, which matters when you buy a mat or frame.

Two common rounded values you will see on packaging: the full sheet as 56 x 76 cm and the quarter sheet as 28 x 38 cm. Both are the exact figures above rounded to the nearest centimeter. If a listing gives a "1/4 size" canvas as 25 x 35 cm or 30 x 40 cm, it is using a different base sheet or rounding freely, and the inch equivalents are 9.8 x 13.8 and 11.8 x 15.7.

How the sheet divides

A full sheet has 660 square inches. Each halving keeps the same paper and simply doubles the count of pieces, which is the easiest way to price a painting surface: a quarter sheet uses exactly one quarter of a full sheet of paper, so if a full sheet of 140 lb Arches costs you $12, the paper under a quarter sheet painting costs $3.

Notice that the proportions drift slightly as you go down. A full sheet is 22:30, which simplifies to 11:15 (a ratio of 1:1.36). A half sheet is 15:22 (1:1.47). A quarter is back to 11:15, and an eighth is 7.5:11 (1:1.47 again). So full and quarter sheets share one shape, and half and eighth sheets share another, slightly longer shape. The A-series avoids this drift by starting from a 1:1.414 ratio that stays constant at every halving; see the A-series size guide for that system.

Full sheets: 22 x 30 inches

Full sheets are sold loose, in packs, and in 22 x 30 pads. Loose sheets from Arches, Fabriano and Saunders Waterford are the professional choice because they are 100 percent cotton and come in three surfaces: hot press (smooth), cold press (light texture) and rough. A 22 x 30 pad is the practical way to buy full sheets if you mostly cut them down, because the pad protects the paper and costs less per sheet than the premium cotton brands. Standard weights at this sheet size are 90 lb (190 gsm), 140 lb (300 gsm) and 300 lb (640 gsm); 140 lb is the everyday weight and 300 lb does not need stretching.

Full sheet pad

Strathmore 300 Series Watercolor Pad, 22 x 30 (full sheet)

Fifteen 22 x 30 cold press sheets at 140 lb in a tape bound pad. Tear one into quarter sheets and you have four 11 x 15 sheets for well under a dollar each.

$27.74 at Amazon →

Half sheets: 15 x 22 inches

Half sheets are the size of most exhibition watercolors and the largest size that fits comfortably on a home drafting table. Pads and blocks at 15 x 22 exist but are less common than the quarter size, so many painters buy full sheets and tear them in half. A half sheet painting fits an 18 x 24 frame with a 1.5 inch mat border at left and right and a 1 inch border top and bottom; our standard frame size chart lists the other frames that work. For canvas, there is no 15 x 22 stretched size; 16 x 20 and 18 x 24 are the nearest stocked sizes, and 18 x 24 is closer in feel.

Quarter sheets: 11 x 15 inches

The quarter sheet is the default watercolor size. Nearly every brand makes an 11 x 15 pad or block: Arches, Strathmore, Canson, Fabriano, Baohong and dozens of others. A block is glued on all four sides so the sheet stays flat while wet and does not need stretching; a pad is glued or tape bound on one side and costs less. If you paint loose and wet, buy the block. If you paint dry or use a board and tape, the pad is the better value.

Quarter sheet block

Strathmore 400 Series Watercolor Block, 11 x 15 (quarter sheet)

Fifteen sheets of 140 lb cold press bound on all four sides, so wet washes dry flat without stretching. The size every watercolor class asks for.

$25.60 at Amazon →

Quarter sheet pad, budget

Strathmore 300 Series Watercolor Pad, 11 x 15 (quarter sheet)

The same 11 x 15 quarter sheet in a tape bound pad at about half the price of a block. Tape it to a board for wet work.

$12.94 at Amazon →

For canvas, a quarter sheet corresponds to the 11 x 14 and 12 x 16 boards. Both are standard US sizes, both fit standard frames, and 11 x 14 canvas panels are sold in packs of a dozen or more at very low prices, which is why they are the usual size for oil and acrylic studies.

Quarter size canvas boards

Simetufy 11 x 14 Canvas Panels, 12 Pack

Twelve primed 11 x 14 panels, the US equivalent of a quarter size canvas board. Under two dollars a board for studies and class work.

$17.99 at Amazon →

Eighth sheets: 7.5 x 11 inches

Eighth sheets are the sketch and study size. Few pads are made at exactly 7.5 x 11; the nearest common pads are 7 x 10 and 8 x 10, and many painters simply tear quarter sheets in half. For canvas, an eighth sheet maps to the 8 x 10 board, the most common small canvas size in the US. An 8 x 10 board is half an inch wider and an inch shorter than a true eighth sheet, which is close enough that the two are treated as the same size in practice.

Eighth size canvas boards

Fredrix Artist Series Canvas Panels, 8 x 10, Pack of 12

A dozen archival 8 x 10 panels from the oldest canvas maker in the US. The eighth size board for plein air and color studies you might want to keep.

$45.00 at Amazon →

Which pads, blocks, boards and frames match each fraction

Use this table to move between paper, canvas and framing. The frame column assumes a mat; a watercolor on a quarter sheet almost always looks better with a 2 to 2.5 inch mat inside a 16 x 20 frame than pressed to the edge of an 11 x 14 frame.

When you are choosing between paper brands at these sizes, the best watercolor paper guide compares the cotton and cellulose papers that come in quarter and full sheets. For a pad that is not watercolor paper, the paper weight conversion chart explains why 140 lb means 300 gsm only at the 22 x 30 sheet size.

Fraction sizes and the metric world

If you buy from a European or Asian shop, you will meet the fractions under metric names. A full sheet is listed as 56 x 76 cm, a half as 38 x 56 cm, a quarter as 28 x 38 cm, and an eighth as 19 x 28 cm. Those are rounded from the exact figures in the table above. Not every maker starts from the 22 x 30 sheet, and some round each fraction to the nearest whole inch or centimeter, so a "1/4 size" board from one brand can be an inch larger or smaller than another brand's. If the fraction on a listing does not match the dimensions here, look for the stated size in inches or centimeters and trust that instead.

For anything larger than a full sheet, the fraction system stops and named sheets take over: double elephant (about 27 x 40 inches, though maker dimensions vary) and the 10 yard roll. For painting at that scale most people switch to canvas, and the large canvas size guide covers the sizes from 30 x 40 up.

Frequently asked questions