Photo Aspect Ratio Calculator
The Photo Aspect Ratio Calculator helps photographers match their images to standard print sizes and social media dimensions. Compare print formats like 4×6, 5×7, 8×10, and 11×14, and calculate the exact crop needed to fit each frame without distortion.
🕐 Recent Calculations
What is Photo Aspect Ratio?
Photo aspect ratio determines how a photograph fits into print frames, social media formats, and digital displays. A photo shot in 3:2 (standard DSLR) must be cropped to 5:4 to fit an 8×10 frame, losing some content at the edges. Understanding photo ratios prevents unexpected cropping.
Common photo print ratios include 3:2 (4×6 prints), 7:5 (5×7 prints), 5:4 (8×10 and 16×20 prints), and 7:5 (5×7 prints). Social media ratios differ: Instagram uses 1:1 and 4:5, Facebook covers use 205:78, and Pinterest pins use 2:3.
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.
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 is a 4×6 photo? ▼
A 4×6 photo has an aspect ratio of 2:3 (or 3:2 in landscape). This matches the standard 35mm camera sensor ratio, so DSLR photos fit 4×6 prints perfectly without cropping.
Why do my photos get cropped when printing 8×10? ▼
Most cameras shoot in 3:2 ratio, but 8×10 prints use 4:5 ratio. The 3:2 is wider, so the sides get cropped to fit the narrower 4:5 frame. Always review the crop preview before printing.
What is the best aspect ratio for portrait photography? ▼
4:5 is popular for portrait photography as it provides more vertical space for head-to-waist framing. It maps perfectly to 8×10 and 16×20 print sizes and is Instagram's preferred portrait format.
How do I resize photos for multiple social media platforms? ▼
Create crops at each platform's native ratio: 1:1 for Instagram feed, 4:5 for Instagram portrait, 9:16 for Stories/Reels, 16:9 for YouTube thumbnails, and 2:3 for Pinterest pins.
What resolution is needed for a large format print? ▼
For prints larger than 24 inches, 150-200 DPI is acceptable because viewers stand farther back. A 24×36 poster at 150 DPI needs 3600×5400 pixels (about 19 MP).