Aspect Ratio Calculator
Instantly calculate the proportional relationship between width and height for any display, video frame, or image. Enter width, height, or a target ratio to find the missing dimension — with support for 16:9, 4:3, 21:9, 1:1, and any custom aspect ratio.
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What is an Aspect Ratio?
An aspect ratio describes the proportional relationship between the width and height of a rectangular shape. Written as W:H, it defines the shape of a screen, image, or video frame without specifying the actual dimensions. For example, the 16:9 aspect ratio used by modern HD televisions means that for every 16 horizontal units, there are exactly 9 vertical units — whether the display is 32 inches or 65 inches diagonally.
Common aspect ratios you will encounter include 16:9 for HDTV and YouTube, 4:3 for classic television and presentations, 21:9 for ultrawide cinema displays, 1:1 for Instagram square posts, and 9:16 for TikTok and Stories content. Maintaining the correct aspect ratio when resizing prevents stretching, squashing, or letterboxing that degrades visual quality.
Formules et Équations utilisées
Ce calculateur s'appuie sur 5 équations fondamentales :
1 Aspect Ratio from Dimensions ▼
Divide both width and height by their GCD. 1920 × 1080: GCD(1920, 1080) = 120. Ratio = 16 : 9.
2 Height from Width and Ratio ▼
Given a width of 1280 and a 16:9 ratio: Height = 1280 × (9/16) = 720 pixels.
3 Width from Height and Ratio ▼
Given a height of 1080 and a 16:9 ratio: Width = 1080 × (16/9) = 1920 pixels.
Explore all calculation options on the Calculateur de Ratio home page.
Comment utiliser ce calculateur
Pour utiliser ce Calculateur de Ratio, suivez ces 3 étapes :
Saisir les Valeurs
Saisissez les valeurs de ratio connues dans les champs. Laissez un champ vide — c'est la valeur manquante que le calculateur va chercher à résoudre.
Choisir le Mode
Sélectionnez le mode de ratio — Résoudre, Simplifier ou Mettre à l'échelle. Chaque mode applique des formules différentes à vos valeurs.
Obtenir les Résultats
Cliquez sur Calculer. L'écran de résultats affiche la réponse avec une barre de ratio interactive, un diagramme circulaire et le détail des calculs.
Exemples Pratiques et Solutions Étape par Étape
Voici 3 exemples de calculs résolus avec les étapes détaillées grâce à ce calculateur :
Saisie 1 Find aspect ratio of 2560 × 1440
Saisie 2 Find height for 1920px wide at 4:3
Saisie 3 Find width for 1080px tall at 21:9
Foire Aux Questions
What is the most common aspect ratio for monitors? ▼
16:9 is the most common aspect ratio for monitors, TVs, and laptops. Standard resolutions include 1920×1080 (Full HD), 2560×1440 (QHD), and 3840×2160 (4K UHD). Ultrawide monitors use 21:9 at resolutions like 3440×1440.
How do I calculate the aspect ratio of my screen? ▼
Divide your screen's pixel width by its height, then simplify by dividing both numbers by their greatest common divisor (GCD). For a 2560×1080 monitor: GCD is 40, giving 64:27 — an ultrawide ratio. Use this calculator to automate the process.
What aspect ratio is best for YouTube videos? ▼
16:9 is the standard YouTube aspect ratio. Upload at 1920×1080 (1080p) or 3840×2160 (4K) for best quality. YouTube will add letterbox bars to videos with different ratios. YouTube Shorts use 9:16 (vertical).
What is the difference between 16:9 and 16:10? ▼
16:9 is wider and flatter, standard for entertainment. 16:10 is slightly taller (about 5.5% more vertical space), common on productivity laptops like MacBook Air (2560×1600). The extra height helps with documents, code, and web browsing.
How do I resize an image without changing its aspect ratio? ▼
Lock the aspect ratio in your editing software (usually a chain-link icon), then change only one dimension. The other adjusts automatically. For example, scaling a 1600×900 image (16:9) to 800px wide automatically sets height to 450px.
What aspect ratio does Instagram use? ▼
Instagram supports multiple ratios: 1:1 (square, 1080×1080), 4:5 (portrait, 1080×1350), and 1.91:1 (landscape, 1080×566). For Reels and Stories, use 9:16 (1080×1920). Portrait 4:5 typically gets the most feed visibility.
How do I convert aspect ratio to pixel dimensions? ▼
Multiply each ratio number by the same scale factor. For 16:9 at 720p: 720 ÷ 9 = 80 (scale factor), then 16 × 80 = 1280. Result: 1280×720. For 4K: 2160 ÷ 9 = 240, then 16 × 240 = 3840. Result: 3840×2160.
What is the aspect ratio of a 4K display? ▼
Standard 4K (UHD) is 3840×2160, which is 16:9. DCI 4K (cinema) is 4096×2160, which is approximately 1.9:1 (256:135). Both are often called '4K' but have different aspect ratios.
Can aspect ratio affect page load speed? ▼
Indirectly, yes. Using the wrong aspect ratio forces browsers to reflow content when images load. Setting explicit width and height attributes (or CSS aspect-ratio) prevents cumulative layout shift (CLS), improving Core Web Vitals scores.
What is anamorphic aspect ratio? ▼
Anamorphic is a cinematography technique that uses special lenses to capture a wider field of view on standard film/sensor. The recorded image is horizontally squeezed and must be stretched during playback. Common anamorphic ratios include 2.39:1 and 2.76:1.
How do I find the aspect ratio of a video file? ▼
Use MediaInfo (free software) or right-click the file and check Properties > Details. Look for 'Frame width' and 'Frame height'. Divide both by their GCD to get the ratio. Most video players also display this in stream information.
What aspect ratio should I use for printing photos? ▼
Standard print sizes use different ratios: 4×6 is 3:2, 5×7 is 5:7, 8×10 is 4:5, and 11×14 is 11:14. Most digital cameras shoot in 3:2, so 4×6 prints require no cropping. Other sizes will need slight cropping.