Image Upscaler
Make a small picture 2, 3 or 4 times bigger with high-quality Lanczos-3 or bicubic resampling, add a touch of sharpening and compare before and after. The image is processed on your device and never uploaded.
Showing a small sample picture
How to use the Image Upscaler
- Add an image: drop it on the box, press Choose image or paste it with Ctrl+V.
- Pick the scale: 2×, 3× or 4×. The output size appears on each button.
- Choose a method: Lanczos-3 for photos and graphics, Bicubic for a softer look, Nearest neighbor for pixel art.
- Turn on Sharpen if the result looks soft, and set the amount.
- Press Upscale image, drag the compare slider or zoom to 100%, then download the result.
How the resampling methods work
Upscaling creates new pixels between the existing ones. Each output pixel is mapped back to a position in the source image, source x = (output x + 0.5) ÷ scale − 0.5, and its color is a weighted average of the nearby source pixels. The methods differ only in how many neighbours they use and how they weight them. The filter runs horizontally first and then vertically, which gives the same result as a full 2D filter but is much faster.
| Method | Neighbours used | Kernel | Best for |
|---|---|---|---|
| Nearest neighbor | 1 | Copy the closest pixel | Pixel art, icons, screenshots at exact 2×/3×/4× |
| Bicubic (Catmull-Rom) | 4 × 4 | Cubic spline, a = −0.5 | Smooth photos, skin, gradients |
| Lanczos-3 | 6 × 6 | sinc(x) · sinc(x/3) for |x| < 3 | Most photos, graphics and text; crispest edges |
The Lanczos-3 weight for a distance x is L(x) = 3 · sin(πx) · sin(πx/3) ÷ (π²x²), with L(0) = 1. Because it has small negative lobes, it keeps edges crisp but can add a faint light or dark outline right next to very hard edges. Transparent images are processed with premultiplied alpha, so edges do not get dark fringes.
Sharpening after upscaling
The optional sharpen step is a classic unsharp mask: the upscaled image is blurred with a Gaussian (radius scaled to the enlargement, sigma ≈ 0.6 × scale), and the difference is added back: result = image + amount × (image − blurred). 25–50% suits most photos; go higher for soft, out-of-focus pictures and lower for noisy or heavily compressed JPGs, where sharpening also makes artefacts more visible.
Output sizes and print guide
| Source | 2× | 3× | 4× |
|---|---|---|---|
| 320 × 240 | 640 × 480 | 960 × 720 | 1280 × 960 |
| 640 × 480 | 1280 × 960 | 1920 × 1440 | 2560 × 1920 |
| 800 × 600 | 1600 × 1200 | 2400 × 1800 | 3200 × 2400 |
| 1024 × 1024 | 2048 × 2048 | 3072 × 3072 | 4096 × 4096 |
For printing, divide pixels by the print resolution: 2400 × 1800 px at 300 DPI prints at 8 × 6 inches. Upscaling helps avoid visible pixels in prints and on large screens, but it cannot invent real detail. To shrink an image instead, use the Image Resizer; to make the result smaller on disk, try the Image Compressor.
Frequently asked questions
Can upscaling add real detail to a photo?
No resampling method can recover detail that was never captured. Lanczos and bicubic estimate the new pixels from their neighbours, which gives smooth, natural edges without blockiness. AI upscalers invent plausible texture, which can look sharper but may also add details that were not there. For logos and text, a vector source (SVG) is always best.
What is the difference between Lanczos-3 and bicubic?
Both are interpolation filters. Lanczos-3 uses a windowed sinc function over 6 × 6 neighbouring pixels and keeps edges crisper, with slight ringing next to very hard edges. Bicubic (Catmull-Rom, a = −0.5) uses 4 × 4 pixels and is a little softer. Nearest neighbor simply repeats pixels, which is ideal for pixel art and icons.
Should I use the Sharpen option?
Enlarged images always look somewhat softer, so a light unsharp mask (25–50%) usually helps photos. Higher amounts make edges pop but can create halos and emphasise noise and JPEG artefacts. Leave it off for pixel art and Nearest neighbor.
What is the maximum output size?
The result can be up to 16.7 megapixels (for example 4096 × 4096) and 8192 pixels on the longest side. That keeps memory use safe and works in every browser, including on iPhone. If a scale would exceed it, the tool tells you and suggests a smaller factor.
Does upscaling help for printing?
It gives the printer more pixels, so the print shows no blocky pixels, but it does not add true sharpness. For a 300 DPI print, a 1200 × 1800 px photo makes a 4 × 6 inch print; upscaling it 2× lets you print 8 × 12 inches with smooth edges, though fine detail stays the same.
Is my image uploaded?
No. The resampling runs in JavaScript in a Web Worker on your own device. Nothing is sent to a server.