How do I calculate height from width and aspect ratio?

Height = Width ÷ (ratio W/H). For 16:9 with width 1280: Height = 1280 ÷ (16/9) = 720.

Aspect Ratio Calculator — Width, Height & Presets

How the Aspect Ratio Calculator Works

Aspect ratio expresses the proportional relationship between width and height. The formula is simple: Width = Height × (W/H), or Height = Width ÷ (W/H). Pick a preset ratio (16:9, 4:3, etc.) or enter a custom ratio, then type either dimension and the other auto-fills.

Lock ratio — enable to keep proportions when typing either dimension.
Custom ratio — type any W:H values, including decimals like 2.39:1 for cinemascope.
Common sizes — click a preset to instantly populate both dimensions (1920×1080, 4K, etc.).

Common Use Cases

Video production is the most common scenario. You're exporting a clip and the editor asks for a 1280×720 master, but your social team needs a 1:1 square crop and a 9:16 portrait for Reels. This tool tells you exactly how many pixels to crop from each edge, and what resolution to export to if you want to maintain sharpness at the target size.

Web design is the second major use. An OG image (Open Graph) should be 1200×630 — that's the 1.91:1 ratio used by Facebook, LinkedIn, and Twitter card previews. Banner images, hero backgrounds, and thumbnail containers all have specific ratios that must be respected to avoid unexpected cropping on different screens.

Photography has its own standards: full-frame sensors produce 3:2 images (as in 35mm film), which is why a standard 4×6 print fits perfectly. Point-and-shoot cameras typically shoot 4:3. When you order prints, selecting the wrong ratio means the lab will crop your image automatically — sometimes cutting off heads or feet.

Common sizes and copy buttons

The calculator ships with the seven ratios you'll use 90% of the time — 16:9, 4:3, 3:2, 1:1, 21:9, 9:16, and 2.39:1 cinemascope. Seven common output sizes are clickable: FHD, HD, 4K, Portrait Reel, QHD, Square, and OG image. Click any size to fill both fields at once. Copy individual values with the copy buttons — useful when pasting into Figma, Premiere, or Photoshop.

What isn't here: pixel density (PPI/DPI) conversion, crop preview graphics, or a scale factor slider. Those add enough complexity that they'd belong in a separate tool. This one stays focused on the single question you actually have: given this ratio and this width, what's the height?

Frequently Asked Questions

What is aspect ratio?

Aspect ratio is the proportional relationship between width and height, expressed as two numbers separated by a colon (e.g., 16:9). A 1920×1080 image and a 1280×720 image both have a 16:9 ratio — the ratio stays the same when you scale while keeping proportions.

What's the difference between 16:9 and 4:3?

16:9 is the standard widescreen format used by modern TVs, YouTube, and most video content. 4:3 was the standard for older TVs and computer monitors — it's squarer. The main practical difference: displaying 4:3 content on a 16:9 screen shows letterbox bars on the sides (pillarboxing), and 16:9 on 4:3 shows bars top and bottom (letterboxing).

What is 2.39:1 used for?

2.39:1 (often called anamorphic or Scope) is used in theatrical films for an ultra-widescreen cinematic look. Many major films — from Lawrence of Arabia to modern blockbusters — are shot in this format. Streaming services often preserve it, which is why you see black bars even on a widescreen TV.

What aspect ratio should I use for Instagram Reels?

Instagram Reels recommend a 9:16 aspect ratio at 1080×1920 pixels. This fills the full phone screen vertically. For a feed post, a 4:5 (1080×1350) or 1:1 square works well. Using the wrong ratio means Instagram may crop or add padding automatically.

How do I calculate the height from a width and ratio?

Height = Width ÷ (ratio W/H). For example, for a 16:9 ratio with width 1280: Height = 1280 ÷ (16/9) = 1280 × (9/16) = 720. Or just enter the width in this calculator and it fills in the height instantly.