印刷用画像サイズ変更 無料オンライン

Open the site, click the blue Upload image button, select your JPG/PNG/TIFF/HEIC/WebP file (up to ~50 MB recommended), then pick the Output format from the dropdown (JPG/PNG/TIFF/PDF). Use the Set dimensions fields to enter physical print size (inches, cm or mm), enter the desired DPI (default 300 DPI for photos), and choose the resample method (Bicubic for photos, Nearest for pixel art). Click Apply resize, wait for the preview to render in your browser, then hit Download to save the print-ready file to your device.

Resize Image for Print Online Free — Print-Ready Photo Resiz accepts JPG, JPEG, PNG, WebP, GIF (first frame), BMP, TIFF and HEIC as inputs, and can export JPG, PNG, TIFF and PDF print-ready files. In-browser performance is best for files up to about 50 MB or images under roughly 8000×8000 pixels; you can try larger files but Chrome/Firefox on desktop handles them more reliably than mobile Safari. The tool will warn if an uploaded file exceeds memory limits and recommends downscaling or using desktop Chrome/Firefox for very large files.

For photographic prints, set DPI to 300 in the DPI input field — this is exposed in the right-hand panel labeled DPI / Print resolution — while 600 DPI can be used for small, highly detailed prints and 150 DPI for large posters viewed at distance. The tool recalculates pixel dimensions automatically when you change physical size or DPI; after typing the new DPI, click Apply resize to regenerate the preview. Note the trade-off: increasing DPI without adding pixels will effectively upscale and can soften or introduce artifacts, so always check the preview and consider exporting TIFF at high quality for further sharpening in Photoshop if needed.

The tool can upscale using selectable resampling algorithms (Bicubic smoother for upscaling, Lanczos where available), but upscaling cannot create genuine detail — it reduces visible pixelation compared with nearest-neighbor but will not match native-resolution prints. If you upscale to a large physical size at 300 DPI and your source lacks sufficient pixels, the preview shows interpolation artifacts; you can choose Higher quality export (JPG quality 90–95% or TIFF) to minimize compression noise, but for best results capture at native resolution or use Photoshop’s Preserve Details 2.0 for advanced upscaling.

The tool supports batch resizing via the Add more images button on the Upload screen and will process up to 10 files per batch comfortably in most browsers, with a combined recommended limit of ~200 MB to avoid browser memory issues. For each image you can set individual dimensions/DPI or apply a common template to all files using the Apply to all switch. If you need larger batches or automation, export resized images and run a desktop batch script or use Photoshop/Lightroom, as this web tool is optimized for small to medium batches in-browser.

Mobile Safari and iOS sometimes present HEIC files differently; when Upload image fails with a HEIC from iPhone, first try Chrome or Firefox on desktop which handle HEIC better, or convert the HEIC to JPG in the Photos app (Share → Save as JPEG) before upload. Resize Image for Print Online Free — Print-Ready Photo Resiz will accept HEIC in many browsers but if conversion occurs it may strip some metadata and ICC profiles, so check the color profile and DPI after conversion. For large HEICs on iOS, you may also hit memory limits — use a desktop browser if you see browser crashes or incomplete uploads.

When you upload an image with an embedded ICC profile (sRGB or Adobe RGB), the tool preserves the profile for TIFF and PDF exports where the browser APIs allow it; for JPG output the processed file is converted to sRGB in most browsers to maximize printer compatibility. You can view and change the output format in the Output format dropdown — choose TIFF or PDF if you need to preserve embedded profiles for a print lab. Always confirm with your print lab which profile they expect, and if necessary export TIFF and send your original ICC file alongside the image.

Browser freezes usually mean you hit in-memory processing limits — resizing very large images (over ~8000×8000 pixels or >50–100 MB) requires a lot of RAM in JavaScript; Chrome and Firefox on desktop handle this better than mobile Safari. To avoid crashes, reduce pixel dimensions slightly before upload, split batches into smaller sets, or use desktop Chrome/Firefox, close other tabs, and increase virtual memory; as a last resort, use a desktop tool like Photoshop which handles very large TIFFs more efficiently. The tool will display an error message suggesting these workarounds when it detects out-of-memory conditions.

The core resize and export happens client-side in your browser for most operations, so image data is not sent to external servers unless you explicitly use a cloud-save feature; there is no signup required and the free workflow produces downloads without watermarks. If you click Save to cloud or Share, those specific actions will transfer files to the chosen service and you’ll be prompted for permissions. For privacy-sensitive work prefer the default local processing and download flow, and double-check that you’re not using any optional upload buttons.

For professional lab prints choose TIFF or high-quality JPG (quality 90–95%) with 300 DPI and the physical dimensions matching the final print; select TIFF if the lab requests it and preserve the embedded ICC profile using the Output format dropdown. For home inkjet printing on photo paper, export JPG at 300 DPI sRGB, set print dimensions to the paper size (e.g., 8×10 inches), and use the printer driver’s color handling set to off if you supply an ICC profile manually. Always confirm bleed and trim: add ~3 mm bleed in the Set dimensions panel if your print requires edge-to-edge printing, then click Apply resize and inspect the preview at 100% zoom.

This web tool is faster for quick, single-image size and DPI changes without installing software: use Upload image → set dimensions/DPI → Apply resize → Download, which is ideal for casual users and small batches. Photoshop offers more control (advanced resampling, layers, high-bit TIFF, soft-proofing and CMYK conversions) and handles very large files and batch automation more robustly, while Acrobat is better for assembling multi-page PDFs with preflight. Use Resize Image for Print Online Free when you need a quick, browser-based resize and export to JPG/TIFF/PDF, but switch to desktop apps for colour-managed, preflighted production work.

Start by uploading the highest-resolution original, set output to TIFF or high-quality JPG, use 300 DPI for photos and 600 DPI for small detailed prints, and apply Bicubic or Lanczos resampling in the Resample dropdown. After resizing, use the Sharpen slider sparingly if available (or sharpen later in Photoshop with Unsharp Mask), export at JPG quality 90–95% or TIFF 16-bit for maximum headroom, and check the 100% preview to spot interpolation artifacts before download. For repeat jobs create and save a template (Apply to all) with your preferred units, DPI and output format to speed future batches.