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アスペクト比計算機
解像度を入力して画面アスペクト比を計算し、比率を保ったままリサイズします。SNS画像サイズのプリセット対応。
px
px
Aspect Ratio
16:9
Widescreen (TV, Monitor)
Resolution
1920 × 1080
Total Pixels
2.07 MP
2,073,600 px
Megapixels
2.07 MP
Resolution Grade
Full HD
Visual Preview
16:9
Common Resolutions
About Aspect Ratio
- • 16:9: Standard ratio for modern TVs, monitors, and YouTube. Used by HD, FHD, and 4K displays.
- • 4:3: Classic ratio used by old TVs and iPads. Good for documents and web browsing.
- • 21:9: Used by cinema screens and ultrawide monitors. Great for immersive gaming and movies.
- • 1:1: Square format, the default ratio for Instagram feed posts.
📖 使い方
- Enter width and height in pixels
- Or select a resolution preset
- View aspect ratio, total pixels, and resolution grade
- Use Resize mode to scale while maintaining aspect ratio
- Use From Ratio mode to calculate dimensions from one known value
✨ 主な機能
- ✓Automatic aspect ratio calculation (16:9, 4:3, 21:9, etc.)
- ✓Various resolution presets (HD to 8K)
- ✓Social media formats (Instagram, YouTube, etc.)
- ✓Resize while maintaining aspect ratio
- ✓Calculate resolution from ratio
- ✓Total pixels and megapixels display
- ✓Resolution grade indicator (SD, HD, FHD, QHD, 4K, 8K)
- ✓Visual aspect ratio preview
📐 計算式
Ratio = Simplify with GCD(width, height) → width÷GCD : height÷GCD💡 計算原理
- •Aspect ratio represents the proportional relationship between width and height, simplified using GCD.
- •Example: 1920×1080 has a GCD of 120, resulting in 16:9.
- •Same ratio can have different clarity and file sizes depending on resolution.
- •Resizing while maintaining ratio prevents image distortion.
- •Different social media platforms have different optimal ratios and resolutions.
❓ よくある質問
Q. What is the difference between 16:9 and 21:9?
A. 16:9 is standard widescreen (TV, YouTube), 21:9 is ultrawide (movies, gaming monitors). 21:9 is wider for better immersion but may have letterboxing on some content.
Q. What is the best ratio for Instagram?
A. Feed square: 1:1 (1080×1080), Portrait: 4:5 (1080×1350), Stories/Reels: 9:16 (1080×1920).
Q. What is the recommended YouTube thumbnail size?
A. 1280×720 pixels (16:9 ratio) is recommended. Minimum should be 640×360.
Q. What is the difference between 4K and FHD?
A. 4K (3840×2160) has 4 times the pixels of FHD (1920×1080). Both are 16:9 but 4K is much sharper.
Q. Does resizing while maintaining ratio affect quality?
A. Downscaling usually has minimal quality loss. However, upscaling can cause blur as pixels are interpolated.
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