Ladder one: US inch sizes
These are the sizes ready-made frames are stocked in across the United States and Canada. They did not come from a standards body; they accumulated. That is why the ratios in the right-hand column are all over the place.
| Size (in) | mm | Ratio | px @ 300 PPI |
|---|---|---|---|
| 4 × 6 | 102 × 152 | 1.500 | 1200 × 1800 |
| 5 × 7 | 127 × 178 | 1.400 | 1500 × 2100 |
| 8 × 10 | 203 × 254 | 1.250 | 2400 × 3000 |
| 8.5 × 11 | 216 × 279 | 1.294 | 2550 × 3300 |
| 11 × 14 | 279 × 356 | 1.273 | 3300 × 4200 |
| 12 × 16 | 305 × 406 | 1.333 | 3600 × 4800 |
| 12 × 18 | 305 × 457 | 1.500 | 3600 × 5400 |
| 16 × 20 | 406 × 508 | 1.250 | 4800 × 6000 |
| 18 × 24 | 457 × 610 | 1.333 | 5400 × 7200 |
| 20 × 30 | 508 × 762 | 1.500 | 6000 × 9000 |
| 24 × 36 | 610 × 914 | 1.500 | 7200 × 10800 |
Millimetre equivalents rounded to the nearest whole mm at 25.4 mm to the inch. Pixel counts are inches × 300, the density normally specified for prints viewed close up. 8.5 × 11 is US Letter, included because it is what a buyer's home printer produces.
Ladder two: the ISO A series
The A series is the opposite kind of object: designed rather than accumulated, defined in ISO 216, and used essentially everywhere outside North America. Every size shares one aspect ratio — √2, about 1.414 — chosen for a specific property: cut any sheet in half across the long side and both halves have the same proportions as the original. A4 is exactly half of A3, which is half of A2, and so on.
| Size | mm | in | px @ 300 PPI |
|---|---|---|---|
| A6 | 105 × 148 | 4.13 × 5.83 | 1240 × 1748 |
| A5 | 148 × 210 | 5.83 × 8.27 | 1748 × 2480 |
| A4 | 210 × 297 | 8.27 × 11.69 | 2480 × 3508 |
| A3 | 297 × 420 | 11.69 × 16.54 | 3508 × 4961 |
| A2 | 420 × 594 | 16.54 × 23.39 | 4961 × 7016 |
| A1 | 594 × 841 | 23.39 × 33.11 | 7016 × 9933 |
| A0 | 841 × 1189 | 33.11 × 46.81 | 9933 × 14043 |
Millimetre figures are the ISO 216 definitions. Inches and pixels are derived from them. Because the millimetre values are themselves rounded, individual sizes land a hair off exactly √2 — A5 computes to 1.419, A0 to 1.414. ISO 216 also sets manufacturing tolerances: ±1.5 mm for dimensions up to 150 mm, ±2 mm from 150 to 600 mm, and ±3 mm above 600 mm.
The column that actually matters
Look at the two ladders together and the practical problem appears. A4's ratio is 1.414. Nothing in the US column is 1.414. 5 × 7 comes closest at 1.400, and it is still visibly different — over an 8-inch width that discrepancy is more than a tenth of an inch of crop, and at poster scale it is inches.
Which means a single artwork file cannot serve both ladders. It has to be cropped, padded, or re-composed. Sorting the sizes by ratio rather than by dimension makes visible what does and doesn't group:
5:4. The classic photo-print family. One file scales cleanly across all of them.
A family of its own. 11×14 is one of the most-sold US frame sizes and it matches nothing else on the list — the usual cause of an unexplained crop.
4:3. The standard poster family and the native ratio of a lot of camera output.
3:2. 35 mm photography's ratio, and the large-format poster ratio.
√2. Seven sizes, one file, no cropping anywhere on the ladder. This is the whole point of the system.
The realistic conclusion for anyone selling printable art: you are not shipping one file, you are shipping one file per ratio family. Four or five versions covers almost the entire market, and each one needs its own composition — a design that centres nicely at 1.25 will have too much dead space at 1.5.
Frame size is not print size
A frame described as 16 × 20 holds a 16 × 20 sheet of glass, not a 16 × 20 visible image. Two things eat into it.
The rebate. The frame's lip overlaps the edge of whatever is behind the glass, because something has to hold the print in. The mat, if there is one, does the same job with a window cut smaller than the print so the print cannot fall through.
How much gets covered is a supplier decision, not a standard, and published figures differ: framing suppliers commonly quote between 1/8 inch and 1/4 inch of overlap per side, which is 1/4 inch to 1/2 inch off each overall dimension. Frame It Easy, for example, states it applies a 1/4 inch overlap by removing 1/2 inch from both the width and the height of the stated art size.
− overlap at 1/4″ per side → opening 7.5 × 9.5 in
visible image loses 0.5 in of width and height
Which is why anything meaningful — a signature, a border, the edge of a subject — needs to sit at least a quarter-inch inside the trim, and why a design whose composition depends on reaching the very edge will disappoint in a frame.
The other direction matters for listings: a matted presentation needs a frame larger than the print. 11 × 14 art in a 16 × 20 frame with a mat is one of the most common ready-made combinations, and a buyer who owns the frame is shopping for the print size, not the frame size. Saying which is which in the listing removes a whole class of returns.
Turning a size into a file
The pixel columns above are just inches × 300. If you need a size that isn't listed, the arithmetic is the same one relationship — pixels ÷ PPI = inches — and DPI vs PPI, explained covers why 300 is the number for arm's-length viewing and why a 24 × 36 poster does not actually need 7,200 pixels of width if it will be seen from across a room. Note how quickly the large sizes escalate: A0 at 300 PPI is a 9,933 × 14,043 pixel image, which is a demanding file to produce and a slow one to upload. Large-format prints are routinely supplied at 150 PPI for exactly this reason.
Two operational notes. Marketplaces cap upload dimensions and file weight, so the master file and the listing image are different objects — Etsy's image sizes and POD file requirements cover those limits. And because buyers cannot judge scale from a photograph, a to-scale size chart is worth more than any number in the description; our wall art size guide generator draws the sizes you actually sell against a room wall at true relative scale and exports it as a listing image.
Sizes deliberately not listed here
Ready-made frame ranges vary by retailer and by country, and this page lists only sizes that are broadly stocked. Square sizes (8×8, 12×12) are common but their ratio is trivially 1.000, so they add nothing to the ratio discussion. The ISO B and C series exist — B is defined as geometric means between A sizes, with B0's short side exactly one metre — but they are almost never used for wall art. Metric poster conventions outside the A series, and Japanese paper sizes, are not covered; we could not verify a single authoritative size list for those and are not going to invent one.
Figures verified July 2026.
Primary sources: ISO 216 — the A-series millimetre definitions A0 to A6, the √2 halving property, and the manufacturing tolerances (±1.5 mm up to 150 mm, ±2 mm from 150–600 mm, ±3 mm above 600 mm), plus the note that the US and Canada are the principal countries not using the system; Frame It Easy, “What is the 1/4″ overlap in custom picture framing?” — the 1/4 inch per-side overlap and the resulting 1/2 inch reduction in each overall dimension, and the alternative 1/8 inch reduced-overlap option; Frame Destination on mat sizing — the narrower 1/8 inch per-side convention, which is why this page gives a range rather than a single figure. The US inch size list is market convention, not a published standard; ratios and millimetre and pixel equivalents are computed from the inch dimensions at 25.4 mm per inch and 300 PPI.