Image Ratio Calculator
Fast, accurate and free online proporcji image calculator tool running directly in your browser.
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Other tools you may find usefulImage aspect ratio calculator – scale dimensions while maintaining aspect ratio
The aspect ratio is the ratio of width to height. Scaling without maintaining proportions = distorted image. The tool calculates the missing dimension based on the other one, maintaining the original proportions. Useful in web, video and print.
Standard aspect ratio
16:9 (1.78:1): HD video standard, YouTube, monitors. 4:3 (1.33:1): old TV and monitors, iPad. 1:1: Instagram, profile photos, icons. 3:2 (1.5:1): cameras (35mm film). 21:9 (2.33:1): ultrawide monitors, cinema. 9:16 (0.56:1): TikTok, Reels, Stories (vertical). 4:5 (0.8:1): Instagram portrait. 2:3 (0.67:1): A4 poster.
Formulas for proportions
Known width, searched height: H = W / (AR_w / AR_h). Known height, searched width: W = H × (AR_w / AR_h). Example 16:9, width 1920px: H = 1920 / (16/9) = 1920 / 1.778 = 1080px. Example 4:3, height 768px: W = 768 × (4/3) = 1024px. Proportional scaling: new W / old W = new H / old H.
Social media proportions
Instagram post: 1080×1080 (1:1), 1080×1350 (4:5 portrait), 1080×566 (1.91:1 landscape). Instagram Stories/Reels: 1080×1920 (9:16). Facebook post: 1200×630 (1.91:1). Twitter/X card: 1200×628. LinkedIn: 1200×627. YouTube thumbnail: 1280×720 (16:9). TikTok: 1080×1920 (9:16). Pinterest: 1000×1500 (2:3).
Aspects in video and screens
Full HD: 1920×1080 (16:9). 4K UHD: 3840×2160 (16:9). 8K: 7680×4320 (16:9). 2K DCI Cinema: 2048×1080 (~17:9). Anamorphic (2.39:1): widescreen cinema. 1440p QHD: 2560×1440 (16:9). Ultrawide 21:9: 2560×1080, 3440×1440. Smartwatch: 1:1. iPhone 15: ~19.5:9. iPad Pro 11": 4.3:3.
Frequently asked questions
How to maintain proportions in CSS?
aspect-ratio: 16/9; (modern CSS property). Padding-top trick (legacy): .wrapper { padding-top: 56.25%; position:relative; } (56.25% = 9/16 = 0.5625). object-fit: contain: scales the image to the container while maintaining aspect ratio. object-fit: cover: fills the container, trims the excess. background-size: contain vs cover: same for background.
How to scale an image proportionally in Photoshop?
Ctrl/Cmd+T (Transform). Hold Shift while dragging a corner (old method). Photoshop 2019+: Shift is not needed - proportions are preserved by default. Enter the W and H values with a chain icon (link icon). Image → Image Size → check "Constrain Proportions".
How to convert proportions in Python?
from fractions import Fraction; r = Fraction(1920, 1080); print(r) → 16/9. New dimensions: W=800; H = int(W * 1080/1920) = 450. Pillow: img.thumbnail((800, 600)) – preserves aspect ratio, fits in 800×600. img.resize((800, 450)) – exactly 16:9. ImageMagick: convert img.jpg -resize 800x450! (! forces) or 800x (width only).
What is letterbox and pillarbox?
Letterbox: black bars up/down – when the content is wider than the screen (16:9 on 4:3). Pillarbox: black bars left/right – when the content is narrower than the screen (4:3 on 16:9). Windowbox: black bars on each side. Anamorphic squeeze: image squeezed for recording, stretched for playback. CSS object-fit: contain adds letterbox/pillarbox automatically.
How to calculate file size after changing resolution?
Uneven relationship: PNG/JPEG file ≠ linear growth. BMP (raw): 1920×1080×3 bytes = ~6MB. JPEG: depends on compression. Rule: file size ≈ proportional to the number of pixels. 2× width and height = 4× more pixels ≈ 4× larger file. Practical: squoosh.app tool for size testing before and after.
Related tools: PPI resolution calculator, pixel to cm converter and file size calculator.