What size frame do I need?

Nearly every framing mistake traces back to answering this question in the wrong order. People choose a frame, then discover what it will and will not hold. The order that works is: measure, decide about matting, then buy.

Step 1: measure the artwork

Use a ruler, not the description it came with. Print sizes drift: a poster sold as 24x36 may measure 23.75 x 35.75, and an art print sold as A3 may have a deckle edge that makes "the size" ambiguous.

Measure both dimensions at two points each — top and bottom, left and right. Paper is not always cut square. If the two measurements differ, record the smaller one, because that is what has to fit.

Note anything that changes the mounting: an embossed seal near an edge, a deckle you want to show, a signature in the bottom margin you must not cover.

Step 2: decide about the mat

This is the actual decision, and it determines the frame size.

Mat it if: the artwork is on paper, it has a signature or margin worth showing, it is going on a wall rather than a desk, or you want it to look considered rather than merely hung. Paper artwork should also be matted for a practical reason — the mat holds it off the glazing, which prevents it sticking in humid conditions.

Skip the mat if: it is a canvas, a poster meant to read edge to edge, a photograph where the composition runs to the border, or the frame is small enough that a border would swallow it.

Step 3: read the size off the table

Unmatted — frame size equals artwork size

Matted — frame size is larger

The standard-border column adds roughly four inches to each dimension; the generous column adds six or more. Both columns are chosen to land on frame sizes that actually exist, which is why some of the arithmetic is slightly uneven.

Step 4: check the shape, not just the size

A frame the right size can still be the wrong shape. This catches people constantly with camera photographs.

A file straight from most cameras is 3:2. The two most commonly stocked frame sizes in the US — 8x10 and 16x20 — are 4:5. Printed to fill an 8x10, a 3:2 photo loses about a fifth of its long edge.

The families worth knowing:

• 3:2 — 4x6, 8x12, 12x18, 16x24, 20x30, 24x36
• 4:5 — 8x10, 16x20, 24x30
• 3:4 — 9x12, 12x16, 18x24, 30x40
• 1:1 — 4x4, 8x8, 12x12, 20x20
• √2:1 — A5, A4, A3, A2, A1

Within a family, any size scales to any other with no cropping. Across families, something gets trimmed. Run your own numbers through the aspect ratio calculator if you are unsure which family you are in — it will list every standard frame that fits your shape.

Step 5: check the wall, not just the frame

The frame size is the artwork opening. The wall gives up the outside dimension, which is the frame size plus twice the moulding width.

For a group of frames, add two to three inches of gap between each one on top of those figures.

When the artwork is a non-standard size

Sooner or later you will have something that is 13.5 x 19, or A3, or a deckle-edged sheet of no fixed size at all. Three routes, cheapest first.

A standard frame with a custom mat. Buy the next standard frame up and have a mat cut to your exact opening. A custom mat costs perhaps fifteen to forty dollars, arrives in a few days, and looks entirely intentional. This is almost always the right answer.

A float mount. Mount the artwork on a backing board slightly smaller than the frame opening, with the artwork's own edges visible and a shadow gap around it. Standard frame, no mat cutting, and it makes a virtue of a deckle edge.

A custom frame. Three to five times the price of a standard one. Correct for a genuinely important piece, excessive for most things.

The one route to avoid is trimming the artwork to fit the frame. It is irreversible, it destroys collectible value, and the cut edge always shows.

Common print sizes and their frames, at a glance

For the sizes people most often arrive with:

Buying for a size you do not have yet

If you are commissioning a print, ordering an enlargement, or choosing what to have made, work backwards: pick the frame size first and print to it.

That inverts the usual order for good reason. Frames are manufactured in a fixed set of sizes; prints can be made at any size at all. Choosing a print size that matches a standard frame costs nothing and saves the entire problem.

The sizes worth printing to, because frames for them are available anywhere: 8x10, 11x14, 16x20, 18x24 and 24x36. Add 12x18 and 20x30 if you are ordering the frame online anyway and want an uncropped 3:2 photograph.