Image Aspect Ratios Explained — 16:9, 4:3, 1:1 and More

Aspect ratio is the relationship between width and height. It determines whether your content looks cinematic, square, or stretched. Getting it wrong means cropped faces, black bars, or distorted images.

The formula

Aspect Ratio = Width : Height (simplified to lowest terms)

To find the ratio:
  GCD = Greatest Common Divisor of width and height
  Ratio = (Width ÷ GCD) : (Height ÷ GCD)

To find dimensions from a ratio:
  If ratio is W:H and you know the width:
    Height = Known Width × (H / W)

Common aspect ratios

Ratio	Decimal	Common use
1:1	1.0	Instagram posts, profile pictures
4:3	1.33	Old TV, iPad screen, PowerPoint
3:2	1.5	DSLR photos, 35mm film
16:9	1.78	YouTube, modern TV, presentations
9:16	0.56	TikTok, Instagram Reels, Stories
21:9	2.33	Ultrawide monitors, cinematic film
2:3	0.67	Pinterest pins, portrait photos

Worked example

Your image is 1920 × 1080 pixels. What’s the aspect ratio?

GCD of 1920 and 1080:
  1920 ÷ 1080 = 1 remainder 840
  1080 ÷ 840 = 1 remainder 240
  840 ÷ 240 = 3 remainder 120
  240 ÷ 120 = 2 remainder 0
  GCD = 120

Ratio = 1920/120 : 1080/120 = 16:9

Now you want to resize to 800px wide while keeping the ratio:

Height = 800 × (9/16) = 450px
New dimensions: 800 × 450

Platform requirements (2024–2026)

Platform	Recommended	Pixels
YouTube thumbnail	16:9	1280 × 720
Instagram post	1:1 or 4:5	1080 × 1080 or 1080 × 1350
Instagram Story/Reel	9:16	1080 × 1920
Facebook cover	2.7:1	820 × 312
Twitter/X post	16:9	1200 × 675
LinkedIn post	1.91:1	1200 × 628
TikTok	9:16	1080 × 1920

When to use aspect ratio calculations

• Resizing images without distortion (maintain the ratio)
• Creating social media templates for multiple platforms
• Setting up video exports in editing software
• Designing responsive layouts that scale proportionally
• Cropping photos for print (8×10, 5×7, 4×6 are all different ratios)

Tips for working with aspect ratios

• “Scale to fit” maintains ratio with possible letterboxing (black bars)
• “Scale to fill” maintains ratio but crops the overflow
• “Stretch” ignores ratio — almost never what you want
• Design at the largest size you’ll need, then scale down (maintains quality)
• CSS aspect-ratio: 16/9 forces elements to maintain ratio in responsive designs
• For print: 4×6 = 2:3, 5×7 = 5:7, 8×10 = 4:5 — they’re all different ratios

Calculate dimensions for any aspect ratio with OurDailyCalc’s aspect ratio calculator — enter width, height, or ratio and get instant resizing options.

TL;DR

• Aspect ratio = width ÷ height, simplified (16:9, 4:3, 1:1)
• 16:9 dominates video; 1:1 and 9:16 dominate social media
• Divide both dimensions by their GCD to find the ratio
• Always resize proportionally — never stretch
• Different platforms require different ratios; design at max size first