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About this tool
Match artwork aspect ratio to standard ISO A-series, imperial and metric frame sizes with crop, mount border and print DPI figures.
Poster Frame Size Matcher compares the aspect ratio of your artwork against off-the-shelf frame openings and reports which stock size fits with the least cropping. It covers the ISO 216 A-series (A5 to A0, all 1 : √2), common imperial openings from 4×6 to 24×36 inches, and metric sizes from 10×15 cm to 70×100 cm, showing the printed size, the leftover mount border and the percentage of image you would lose to fill each frame. Useful before you order a print, because the cheapest framing is always a ready-made frame your image already fits.
Open Poster Frame Size Matcher on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Sorts by shape mismatch, so the frames that need no cropping surface at the top.
Set a minimum mount width and the printed size adjusts to leave that border on every edge.
Shows the DPI you actually get at the printed size and the pixels needed for a clean 300 DPI print.
Standard 3:2 openings are 4×6, 8×12, 12×18, 20×30 and 24×36 inches, plus 10×15 and 20×30 cm in metric. A-series frames are not 3:2 — A4 is 1 : 1.414 — so a 3:2 photo in an A4 frame needs about 6% cropped off the long side or a mount to make up the difference.
Because the ISO 216 A-series uses a 1 : √2 ratio (roughly 1 : 1.414), while most cameras shoot 3:2 (1 : 1.5) and phones often shoot 4:3. The shapes are close but not equal, which is why an A4 print of a camera file always leaves a thin strip of white or loses a strip of image.
At 300 DPI you need about 118 pixels per centimetre, so a 50×70 cm print wants roughly 5900 × 8270 pixels. Large posters viewed from a distance are commonly printed at 150 DPI, which halves that requirement — the tool shows the resolution you would actually achieve at the chosen frame size.
Add a mount when the subject reaches the edge of the frame or the crop would exceed roughly 10% of the image; crop when the composition has spare margin. A mount also keeps the print off the glass, which is why conservation framers use one regardless of ratio.
Add the Poster Frame Size Matcherwidget to your blog or website — free, responsive, no signup. Just keep the “Widget by AltFTool” credit link visible.
<iframe src="https://www.altftool.com/embed/widget/poster-frame-size-matcher"
title="Poster Frame Size Matcher — free AltFTool widget"
width="100%" height="640" style="border:0;border-radius:12px;overflow:hidden"
loading="lazy" referrerpolicy="no-referrer-when-downgrade"></iframe>
<p style="font-size:12px;margin:4px 0 0">Widget by <a href="https://www.altftool.com/tools/all/poster-frame-size-matcher?utm_source=embed&utm_medium=widget">AltFTool — free online tools</a></p>