Resize Images to 3840×2160
Resize images to 4K Ultra HD resolution (3840×2160 pixels). For high-resolution displays, large prints, and professional use. Images smaller than 4K will not be upscaled.
Drop images or folders here, or
Up to 20 files, or 50 from a folder. 50 MB each.
Images will be scaled to fit within 3840×2160 while preserving aspect ratio.
Ctrl+Z undo · Ctrl+Y redo
Preserve camera info, GPS, and other metadata
Need custom dimensions? Full resizer
When to Use 4K Ultra HD
4K is used for large displays, digital signage, professional photography, and high-resolution prints. Only useful if your source image is larger than 4K.
Tips for 4K Ultra HD Images
4K images can be very large files. Use WEBP or AVIF format to keep file sizes manageable. Strip metadata to save additional bytes.
Frequently Asked Questions
Will my phone photo be upscaled to 4K?
No. KoalaPic never upscales images. If your photo is 4032×3024, it will be resized to fit within 3840×2160. If it’s already smaller, it stays at its original size.
What format is best for 4K images?
WEBP or AVIF give the best compression for large images. A 4K WEBP file is typically 40–60% smaller than an equivalent JPG with no visible quality difference.