Aspect Ratio Calculator
Calculate aspect ratios instantly. Convert dimensions, solve for missing sides, and browse 2025/2026 social media image sizes.
Solve for Missing Side
Enter a ratio and one dimension to calculate the other.
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, expressed as W:H (e.g. 16:9). It describes shape, not size — 1920x1080 and 640x360 both have a 16:9 ratio.
How do I maintain aspect ratio when resizing?
Use the solver: enter your ratio and the known side. The calculator solves for the missing dimension using cross-multiplication, ensuring the ratio stays exact.
What aspect ratio should I use for social media?
It depends on the platform. Instagram square posts use 1:1, stories use 9:16, YouTube thumbnails use 16:9, and Twitter/X posts use 16:9. Check the Social Media Sizes tab for full 2025/2026 reference.