Aspect Ratio Calculator
Find the aspect ratio of an image or screen from its width and height in pixels, see the nearest standard ratio (16:9, 4:3, 3:2, 4:5…), and get the matching height for a new width so you can resize without stretching.
Last updated: May 2026
Aspect ratio
16:9 · 1.778:1 · 1280 × 720 px at the new width
Formula below · 1 source (Wikipedia)
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About this calculator
An aspect ratio is the proportion of width to height. The calculator divides both sides by their greatest common divisor:
1920 × 1080 → gcd 120 → 16:9
It also prints the decimal ratio (width ÷ height, 1.778:1 for 16:9), which is how cinema formats are usually written (1.85:1, 2.39:1).
When the exact ratio has large numbers, the image is almost always a standard ratio that was cropped or rounded by a few pixels. 1366 × 768, a common laptop screen, is exactly 683:384, which is within 0.1% of 16:9, so the calculator shows "≈ 16:9". It names the nearest standard ratio when it is within 1%.
To resize without stretching, keep the ratio: new height = new width × height ÷ width, rounded to whole pixels.
Common ratios: - 3:2: most interchangeable-lens cameras (35 mm film and APS-C/full-frame sensors) - 4:3: Micro Four Thirds, most phone cameras, older monitors - 16:9: HD and 4K video, most screens and YouTube - 1:1: square posts - 4:5: tall Instagram feed posts (1080 × 1350) - 9:16: vertical video (Reels, TikTok, Shorts), 1080 × 1920 - 5:4: 8 × 10 in prints - 2.39:1: anamorphic widescreen cinema
How to use
Enter the width and height in pixels (from your photo app's file info or your export settings), then the width you want to resize to. Example (the defaults): 1920 × 1080. The greatest common divisor is 120, so the ratio is 1920 ÷ 120 : 1080 ÷ 120 = 16:9, or 1.778:1. Resized to 1280 px wide it is 1280 × 1080 ÷ 1920 = 720 px tall. Example 2: a 6000 × 4000 photo from a full-frame camera is 3:2 (1.5:1). To post it as a 1080 px wide image keep it 1080 × 720, or crop it to 4:5 (1080 × 1350) for a taller feed post. Example 3: 1366 × 768 is exactly 683:384 and shows as ≈ 16:9 because 1.7786 is within 0.05% of 1.7778.
Frequently asked questions
How do I calculate an aspect ratio by hand?
Divide the width and the height by their greatest common divisor. For 1920 × 1080 the largest number that divides both is 120, giving 16 and 9, so the ratio is 16:9. For the decimal form divide width by height: 1920 ÷ 1080 = 1.778, written 1.78:1.
What aspect ratio should I use for Instagram, YouTube and TikTok?
YouTube and most video players use 16:9 (1920 × 1080 for HD, 3840 × 2160 for 4K). Vertical video for Reels, TikTok and YouTube Shorts is 9:16 (1080 × 1920). For Instagram feed photos, 4:5 portrait (1080 × 1350) takes the most screen space; 1:1 square (1080 × 1080) and 1.91:1 landscape are also accepted. Platforms change their crops from time to time, so check the current guidance before a big campaign.
Why does my camera shoot 3:2 but my print is 8 × 10?
Most interchangeable-lens cameras use the 3:2 shape of 35 mm film, while 8 × 10 in is 5:4. A 3:2 image is longer, so printing it at 8 × 10 crops about 17% of the long side. Use 8 × 12 in (or 4 × 6, 12 × 18, 20 × 30) to print a 3:2 image uncropped.
What is the difference between 16:9 and 16:10?
16:10 (1.6:1) is slightly taller than 16:9 (1.78:1). Many laptops use 16:10 (1920 × 1200, 2560 × 1600) because the extra height helps with documents; video made for 16:9 shows thin black bars on a 16:10 screen.
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