# Aspect Ratio Calculator

> Free aspect ratio calculator. Convert width × height to a ratio, solve for missing dimensions, and look up social media sizes for Instagram, TikTok, YouTube.

- **Category:** Calculators
- **URL:** https://www.teafun.cyou/tools/aspect-ratio/
- **Privacy:** Runs entirely in your browser — no uploads, no account, no tracking.
- **Also known as:** resize ratio, image ratio, width height ratio
- **Related tools:** [Monitor Refresh Rate](https://www.teafun.cyou/tools/monitor/), [Floor Plan Tool](https://www.teafun.cyou/tools/floor-plan/), [Invoice Generator](https://www.teafun.cyou/tools/invoice-generator/)
- **Tags:** Display, Design, Layout

## About

Calculate aspect ratios instantly. Convert dimensions, solve for missing sides, and browse 2025/2026 social media image sizes.

## How to Use the Aspect Ratio Calculator

Open the **Calculator** tab. Enter width and height in pixels — the simplified ratio appears live with the GCD shown. To solve a missing side: enter a target ratio (e.g., `16:9` or `1.78`) and one dimension; the other computes via cross-multiplication. The visual preview renders a scaled rectangle in the chosen ratio so you can sanity-check before exporting. Switch tabs to **Social Media Sizes** for a one-tap copy of current platform dimensions (auto-updated against each platform's spec page). The **CSS Snippet** tab generates the `aspect-ratio` CSS property declaration plus `object-fit` and `object-position` fallbacks for older browsers — paste straight into your stylesheet. The **Image fit** comparator on the right shows `cover` (fill the box, crop overflow), `contain` (letterbox to fit), `fill` (stretch to fit, distorts), `scale-down` (smaller of contain/none), and `none` (no resize) side-by-side on a sample image — useful for picking the right CSS value when your image and container ratios don't match.

## Why Aspect Ratios Matter for Every Screen

Mismatched aspect ratios cause the two most-flagged Core Web Vitals failures: Cumulative Layout Shift (CLS) when an image loads at a different ratio than the placeholder predicted, and Largest Contentful Paint (LCP) when the hero image must be re-laid out mid-paint. The fix is the `aspect-ratio` CSS property (or width/height attributes on `<img>`) which lets the browser reserve the right box before the image bytes arrive. On the social side, Instagram crops anything not 4:5 or 1:1 in feed view; TikTok crops anything not 9:16 in the For You feed; YouTube Shorts requires 9:16 between 1080x1920 and 720x1280 — uploading a 16:9 file gets pillarboxed with black bars and slashes engagement by 30-40% versus a native-ratio upload (per Meta and TikTok 2024 creator-success reports). Print is unforgiving too: a 3:2 photo printed to a 4:6 frame loses 8% of the image to bleed if you do not pre-crop. The calculator's job is to surface the mismatch before you spend an hour fixing it after the fact.

_SEO title: Aspect Ratio Calculator — Social Media Sizes | TeaFun_

## FAQ

### 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.