Resolution Scale & Aspect Ratio Calculator

About Resolution Scale & Aspect Ratio Calculator

The Resolution Scale & Aspect Ratio Calculator is a free, browser-based tool for resizing and reasoning about resolutions. Scale a resolution up or down by percentage while keeping the aspect ratio — the resolution-scaler workflow — or compute a missing dimension from a W:H ratio, reduce a pixel width×height to its simplest ratio, and crop one image to several platform aspect ratios at once. It shows megapixels, recognizes common ratios by name (16:9 Widescreen, 9:16 Shorts/Reels/TikTok, 21:9 Cinematic and more), flags which scales land on even pixels (clean for 4:2:0 video) versus a half-pixel, and ships presets for 720p, 1080p, 1440p, 4K and 8K. Everything runs locally in your browser — instant, nothing uploaded, no signup.

How to use Resolution Scale & Aspect Ratio Calculator

1. Pick a mode at the top: 'Ratio → dimension', 'W×H → ratio', 'Scale', or 'Multi-crop'.
2. To scale a resolution by percentage, choose 'Scale', enter the source width and height, keep 'Percentage', then drag the slider or type a percent (or tap 25/50/75/100/150/200%) — both dimensions scale together so the aspect ratio is preserved.
3. Use the 'Pixel-clean scales' list to pick a percentage whose width and height both stay even (no half-pixels) — important for 4:2:0 video.
4. In 'Ratio → dimension', type a custom W:H (e.g. 16 and 9) and one known dimension to compute the other; in 'W×H → ratio', enter pixels to get the simplified ratio, decimal, common name and megapixels (set the Pixel Aspect Ratio away from 1 for anamorphic content).
5. Click a preset (720p, 1080p, 1440p, 4K UHD, 8K, IG Portrait, etc.) to fill the fields, or use the video probe to auto-fill dimensions from a video file.
6. For 'Multi-crop', drop one image, pick a crop anchor and PNG/JPG format, tick the target ratios (16:9, 9:16, 1:1, 4:5, 4:3), then save crops individually or 'Download all as ZIP'.

Frequently asked questions

How do I scale a resolution by percentage?

Open the Scale mode, enter the source width and height, keep 'Percentage', then drag the slider or type a percent (or use the 25/50/75/100/150/200% buttons). Both width and height scale by the same factor, so the aspect ratio stays the same — for example, scaling 1920×1080 to 50% gives 960×540.

What scales avoid half pixels in video?

The 'Pixel-clean scales' list shows which common percentages keep both width and height whole and even — for 1920×1080, 50% (960×540) and 75% (1440×810) are even, while 66.7% lands on a fractional pixel. Even dimensions encode cleanly for 4:2:0 chroma subsampling; odd or fractional sizes force the encoder to pad or round.

How do I upscale 1080p to 4K dimensions?

1080p (1920×1080) to 4K UHD (3840×2160) is exactly a 200% scale — both dimensions double and the 16:9 ratio is unchanged. Set the source to 1920×1080 and use the 200% button, or pick the 4K UHD preset. Upscaling can't add real detail, but the target dimensions and ratio are computed exactly.

Are my images or data uploaded to a server?

No. All ratio and scaling math runs in your browser, and in Multi-crop mode the image is decoded and cropped on a local canvas on your device — it never leaves the browser and nothing is uploaded.

What is the Pixel Aspect Ratio (PAR) field for?

Leave it at 1 for normal square-pixel media. Set it to a non-1 value (e.g. 1.4222 / 64:45 for DV-PAL 16:9) for anamorphic, non-square-pixel content, and the tool also shows the displayed shape (DAR), which equals the stored ratio multiplied by the PAR.

Is it free and do I need an account?

Yes, it's completely free with no signup, account, or watermark — every calculation runs on your device.

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