Image Aspect Ratio Calculator
Calculate the exact aspect ratio of any image from its pixel dimensions, or find the perfect resize dimensions that maintain the original ratio. Prevent distortion, optimize for social media platforms, and ensure your images display flawlessly across every screen and print format.
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What is Image Aspect Ratio?
The image aspect ratio is the proportional relationship between an image's width and height, expressed as a simplified ratio like 3:2, 4:3, or 16:9. A 4000×3000 pixel photograph has a 4:3 aspect ratio — for every 4 units of width, there are 3 units of height. Maintaining this ratio during resizing ensures the image is never stretched, squeezed, or distorted.
Different use cases demand different aspect ratios: social media profiles (1:1 square), Instagram posts (4:5 portrait), YouTube thumbnails (16:9 landscape), Pinterest pins (2:3 tall), print photos (3:2, 5:7, 4:5), and website banners (custom wide ratios). This calculator determines your image's ratio and computes the exact dimensions for any target ratio or size constraint.
使用される計算公式・方程式
この計算ツールは5つの主要な公式を使用しています：
1 Image Aspect Ratio ▼
A 6000 × 4000 image: GCD = 2000, so ratio = 3 : 2. This is the standard DSLR sensor ratio.
2 Proportional Resize (New Height) ▼
Resizing a 4000×3000 image to 1200px wide: New Height = 1200 × (3000/4000) = 900 pixels.
3 Megapixel Calculation ▼
A 6000 × 4000 image = 24,000,000 pixels = 24 megapixels.
Explore all calculation options on the 比率計算ツール home page.
比率計算ツールの使い方
この比率計算ツールは、以下の3ステップで簡単にご利用いただけます：
数値を入力
入力欄に既知の比率の値を入力します。求めたい未知数の入力欄は空欄のままにしておきます。
モードを選択
比率モード（解く、簡素化、スケーリング）を選択します。各モードで異なる計算式が適用されます。
結果を確認
計算するボタンを押します。結果画面に答えと、視覚的な比率バー、円グラフ、詳細なステップバイステップの解決プロセスが表示されます。
実例問題と段階的な解説
本比率計算ツールを使って、以下の3つの例題をステップバイステップで解決するプロセスです：
入力 1 Find aspect ratio of a 5184 × 3456 image
入力 2 Resize a 4032 × 3024 photo to 800px wide
入力 3 Calculate megapixels of 7680 × 4320
よくある質問 (FAQ)
What aspect ratio is a standard photo? ▼
Most DSLR cameras capture images in 3:2 aspect ratio (e.g., 6000×4000 or 4000×2667). Smartphones typically use 4:3 (e.g., 4032×3024). Medium format cameras often shoot 4:3 or 3:2. The 3:2 ratio matches standard 4×6 inch prints exactly.
How do I find the aspect ratio of my image? ▼
Divide the width by the height, then simplify. A 4032×3024 image: divide both by GCD (1008) = 4:3. A 6000×4000 image: divide both by GCD (2000) = 3:2. Or simply enter the dimensions into this calculator for instant results.
What aspect ratio is best for Instagram? ▼
Instagram supports 1:1 (square, 1080×1080), 4:5 (portrait, 1080×1350), and 1.91:1 (landscape, 1080×566) in the feed. Reels and Stories use 9:16 (1080×1920). Portrait 4:5 typically gets the most feed real estate and highest engagement.
How do I resize an image without losing quality? ▼
Always resize down (make smaller), never up significantly. Maintain the original aspect ratio by locking proportions. Use high-quality resampling algorithms (Lanczos, bicubic) in your image editor. Save in appropriate format: JPEG for photos, PNG for graphics with transparency, WebP for web optimization.
What aspect ratio does a 4×6 print use? ▼
A 4×6 inch print uses a 3:2 aspect ratio (6÷2=3, 4÷2=2). This matches standard DSLR sensor proportions, so 3:2 images print at 4×6 without any cropping. At 300 DPI print resolution, you need at least 1200×1800 pixels.
How do I convert a 16:9 image to 4:3? ▼
You must crop the sides (for landscape) because 16:9 is wider than 4:3. From a 1920×1080 (16:9) image: keeping the full height of 1080, the new width = 1080 × (4/3) = 1440. Crop 240 pixels from each side. Important content should be centered.
What image aspect ratio is best for websites? ▼
It depends on the use case. Hero banners: 16:9 or 21:9 (wide). Blog post images: 16:9 or 3:2. Product images: 1:1 or 4:3. Background images: match the viewport ratio. Set explicit width and height to prevent layout shift. Use srcset for responsive delivery.
Why does my image look stretched on social media? ▼
The platform is forcing your image into a different aspect ratio container. For example, uploading a 3:2 landscape image where the platform displays 1:1 squares causes visible stretching. Always crop to the platform's required ratio before uploading.
What is the difference between image aspect ratio and resolution? ▼
Aspect ratio is the shape (the proportional relationship, e.g., 3:2). Resolution is the total pixel count (e.g., 6000×4000 = 24 megapixels). Multiple resolutions share the same aspect ratio: 1920×1280, 3840×2560, and 6000×4000 are all 3:2.
How do I calculate the pixel dimensions for a custom aspect ratio? ▼
Multiply each ratio number by the same scale factor. For a 5:4 image at 2000px wide: Height = Width × (4÷5) = 2000 × 0.8 = 1600px. For a 5:4 image at 1200px tall: Width = Height × (5÷4) = 1200 × 1.25 = 1500px.
What aspect ratio should I use for YouTube thumbnails? ▼
YouTube thumbnails use 16:9 aspect ratio at 1280×720 pixels (720p). This is the minimum recommended resolution. For sharper thumbnails on high-resolution displays, use 1920×1080. Keep important text and faces in the center 80% (title-safe area).