How to Choose the Right Size Poster Frame | Match Your Print Perfectly

The right poster frame size comes down to matching the frame’s inner aperture to your poster’s exact dimensions, then deciding whether you want a mat border or a flush fit.

A frame that’s slightly too small or built for a mat you don’t want turns a $30 poster into a $60 headache. The fix is one measurement and one decision: flush fit or matted. Measure your poster’s width and height at the widest and tallest points with a rigid tape measure — no cloth tapes — and round to the nearest 1/16 inch. That number is your target aperture size.

Standard Poster Frame Sizes in the US

Most US frames are sold by the print size they’re designed to hold, not their outer dimensions. These are the standard sizes you’ll find at retailers, aligned with common poster printing dimensions:

• 11×17 inches – Small posters, flyers, study aids
• 18×24 inches – Medium concert prints and art reproductions
• 24×36 inches – The most popular size for concert posters, large prints, and home decor
• 27×40 inches – Standard movie poster size
• 16×20, 20×24, 8.5×11 inches – Other common options

If you have a 24 x 18 inch poster that needs fitting, note that this is a less common orientation for that label — always verify the inner opening matches your print’s actual proportions. European A-series prints need millimeter-to-inch conversion (divide by 25.4), then match to the nearest US standard or order custom.

Flush Fit vs. Matting: What Changes

Your choice of matting changes which frame size you buy. A flush fit needs a frame whose inner aperture exactly matches the poster’s dimensions. No mat, no extra allowance — the print sits directly behind the glazing.

With a mat, you need a frame 2–4 inches larger per dimension. For example, a 16×20 poster matted with a 2-inch border needs a 20×24 or 20×28 frame. The mat’s opening is cut slightly smaller than the artwork to overlap the edges, so measure the outer dimensions of the mat board itself, not the artwork.

For a balanced border — say 1 inch on all sides — add 2 inches total to both width and height (1 inch × 2 sides). That gives you the frame aperture size to order.

Common Mistakes and How to Avoid Them

Three errors account for most frame returns. First, buying a frame labeled 18×24 but checking only the outer size — the aperture may be smaller due to beveling or frame lip overlap. Always confirm the inner opening. Second, failing to account for mat width, which leaves you with a frame too small for the matted piece. Third, using a flexible cloth tape, which stretches and produces inaccurate measurements.

One more: including unwanted borders in your measurement. If the poster has a white border you plan to hide behind the frame lip, measure only the visible printed area. That keeps the frame from looking oversized.

Specs That Matter Beyond Size

Three details separate a good frame from a frustrating one. Frame depth determines whether your canvas or layered mat fits inside — thick canvases may need a deeper frame. IKEA’s guide to choosing a picture frame explains how to check depth and compatibility. UV-protective glass prevents your poster from fading over years of display; acrylic is lighter and safer for large frames (24×36 and up).

For wall hanging, frames 24×36 or larger need two hanging points or a French cleat — a single hook can sag. In humid areas, avoid PVC-based mats and glazing; choose acid-free archival materials to prevent poster degradation. Custom frames handle non-standard sizes (like 22×28) but typically cost $80–$250+ and are non-returnable, so verify your measurements twice.