Photo Aspect Ratio Calculator
Calculate the perfect crop dimensions for any photo print size, social media platform, or display format. Enter your photo's pixel dimensions to see its native ratio, then find exact crop coordinates for standard print sizes, Instagram, Facebook, Pinterest, and any custom target ratio.
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What is Photo Aspect Ratio?
Every photograph has a native aspect ratio determined by the camera sensor that captured it. DSLR cameras shoot in 3:2 (6000×4000), smartphones in 4:3 (4032×3024), and medium format cameras in 4:3 or 3:2. When printing, publishing online, or displaying on screens with different ratios, photographers must crop strategically to fit the target format without losing important visual elements.
Understanding photo aspect ratios prevents the two most common problems in photography: unwanted cropping at the print lab (cutting off heads or critical composition elements) and image distortion when forced into social media containers. This calculator bridges the gap between your camera's native ratio and every output format you need, ensuring your images look exactly as intended everywhere they appear.
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 Print Size to Aspect Ratio ▼
An 8×10 print has a ratio of 8:10 = 4:5. A 4×6 print has a ratio of 4:6 = 2:3.
2 Crop Dimensions for Target Ratio ▼
To crop a 6000×4000 photo to 5:4: Crop Height = 6000 × (4/5) = 4800. Since 4800 > 4000, crop width instead: Crop Width = 4000 × (5/4) = 5000.
3 DPI Calculation for Print ▼
A 6000px wide image printed at 8 inches = 6000/8 = 750 DPI. For quality printing, DPI should be at least 300.
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 Crop a 3:2 photo for an 8×10 (5:4) frame
入力 2 Calculate DPI for a 5×7 print from a 4200×3000 image
入力 3 Find the crop for Instagram 4:5 from a 4:3 photo
よくある質問 (FAQ)
What aspect ratio do DSLR cameras shoot in? ▼
Most DSLR cameras (Canon, Nikon, Sony full-frame and APS-C) shoot in 3:2 aspect ratio. Common resolutions include 6000×4000, 6720×4480, and 8640×5760. Micro Four Thirds cameras (Olympus, Panasonic) shoot in 4:3 at resolutions like 5184×3888.
What is the aspect ratio of a 4×6 print? ▼
A 4×6 print has a 3:2 aspect ratio (6÷2=3, 4÷2=2), which matches standard DSLR sensors perfectly. This means DSLR images print at 4×6 without any cropping. At 300 DPI, you need at least 1200×1800 pixels.
How much cropping occurs when printing an 8×10 from a 3:2 image? ▼
An 8×10 print uses a 4:5 ratio (wider than 3:2 in the narrow dimension). A 6000×4000 (3:2) image cropped to 4:5 becomes 5000×4000, losing 500 pixels (8.3%) from each side. Important subjects near the edges may be cropped out.
What ratio is best for Instagram photos? ▼
Instagram supports 1:1 (square, 1080×1080), 4:5 (portrait, 1080×1350), and 1.91:1 (landscape, 1080×566). The 4:5 portrait ratio typically performs best because it takes up the most screen space in the feed, increasing visibility and engagement.
How do smartphone cameras compare to DSLR aspect ratios? ▼
Most smartphones shoot in 4:3 by default (e.g., 4032×3024 on iPhone). Some offer 16:9 mode, which crops the sensor. DSLR sensors are 3:2, which is slightly wider. When printing smartphone photos at 4×6 (3:2), slight cropping is needed.
What is the best aspect ratio for a photo portfolio website? ▼
For consistent gallery presentation, standardize on one ratio per gallery section. Landscape galleries work well at 3:2 (matches most DSLR output). Portrait galleries at 2:3 or 4:5. Mixed galleries can use 4:3 as a middle ground. Consistency matters more than the specific ratio chosen.
How do I calculate print size from pixel dimensions? ▼
Divide pixel dimensions by the print DPI (typically 300 for photo quality). A 6000×4000 image at 300 DPI prints at 20×13.3 inches maximum. At 150 DPI (acceptable for viewing distance above 2 feet), it prints at 40×26.7 inches.
What aspect ratio should I use for framing photos? ▼
Standard frame sizes use these ratios: 4×6 = 3:2, 5×7 = 5:7, 8×10 = 4:5, 8.5×11 = 17:22, 11×14 = 11:14, 16×20 = 4:5. Mat boards can adapt images to different frame sizes, but the image itself must be cropped to match the mat opening ratio.
Can I change a photo's aspect ratio without cropping? ▼
Technically, only by adding canvas (white/black borders, blurred extensions, or AI-generated fill). This changes the image dimensions without removing content. Adobe Photoshop's Generative Fill and Content-Aware Fill can extend edges intelligently. Pure resizing without cropping or extension will distort the image.
What ratio does a 35mm film negative use? ▼
35mm film has a 3:2 aspect ratio (36mm × 24mm). This is why DSLR sensors — designed after 35mm film — also use 3:2. The 4×6 print size was established to match 35mm film proportions without cropping.
How do I choose between portrait and landscape for a print? ▼
Match the orientation to the subject: landscapes, cityscapes, and group photos typically work best in landscape (horizontal). Portraits, full-body shots, and tall architecture work best in portrait (vertical). Some compositions work in both — crop each to evaluate before committing.