Aspect Ratio Calculator
Calculate aspect ratios, resize dimensions while keeping the ratio, or find the missing width or height for any ratio. Click a preset to get started.
Common ratios
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Common aspect ratios
Frequently Asked Questions
What is 16:9 aspect ratio in pixels?↓
16:9 is the standard widescreen ratio used for HD video, YouTube, and most modern monitors. Common 16:9 resolutions include 1280×720 (HD), 1920×1080 (Full HD), 2560×1440 (2K/QHD), and 3840×2160 (4K UHD). To find any 16:9 height, divide the width by 16 and multiply by 9. For example, for a 1600px-wide image: 1600 ÷ 16 × 9 = 900px.
How do I calculate an aspect ratio from dimensions?↓
Divide the width by the height to get the decimal ratio, then find the greatest common divisor (GCD) of the two numbers and divide both by it to get the simplified ratio. For example, 1920×1080: GCD(1920,1080) = 120, so 1920÷120 = 16 and 1080÷120 = 9, giving 16:9. You can do this instantly with the NJHTools Aspect Ratio Calculator at www.njhouse.kr/tools/aspect-ratio.
How do I resize an image and keep its aspect ratio?↓
If you know the original width and height, fix one dimension (width or height) and scale the other proportionally. The formula is: new height = new width × (original height ÷ original width), or new width = new height × (original width ÷ original height). Use the NJHTools Aspect Ratio Calculator in 'Dimensions → Ratio' mode: enter the original size, fix the width or height, enter the target value, and the calculator gives you the missing dimension.
What aspect ratio is best for Instagram?↓
Instagram supports several ratios depending on post type. Square posts use 1:1 (e.g. 1080×1080). Landscape posts use 1.91:1 (roughly 16:9, e.g. 1080×566). Portrait posts use 4:5 (e.g. 1080×1350), which takes up the most vertical space in the feed. Stories and Reels use 9:16 (e.g. 1080×1920).
What is the difference between 16:9 and 16:10?↓
16:9 (decimal 1.778) is the standard for HD and 4K televisions, YouTube videos, and most consumer monitors. 16:10 (decimal 1.6) is slightly taller and was popular in MacBook and WUXGA professional monitors — the extra vertical space is useful for productivity and coding. 16:10 resolutions include 1280×800, 1440×900, 1680×1050, and 1920×1200.
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