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Aspect ratio calculator
Convert pixel dimensions into a clean aspect ratio, reverse-calculate missing width or height from a target ratio, and compare common cinema, monitor, and phone formats — all in your browser.
Ratio Calculator
Width, height, and simplified ratio.
- Aspect Ratio
- 16:9 Standard Wide
- Decimal
- 1.778
Common Ratios
Load a standard format into the calculator.
Dimension Resolver
Height 1080 px
- Full Size
- 1920 × 1080
Pixel Info
- Total Pixels
- 2,073,600
- Megapixels
- 2.07 MP
- Aspect Ratio
- 16:9
- Shape
- Landscape
Aspect ratio calculator tool
Simplify width × height to W:H, read decimal ratios, resolve a missing side, and compare 16:9, 21:9, 9:16, and more — no install required.
Ratio from any resolution
Enter pixel width and height to get a clean aspect ratio and decimal. The preview outline updates so you can see landscape, portrait, or square framing.
Common format presets
Load 16:9, 16:10, 21:9, 4:3, 1:1, 9:16, 3:2, and 32:9 with familiar pixel sizes so you can compare shapes quickly.
Dimension resolver
Know only one side? Lock Known width or Known height and calculate the missing dimension from the active ratio.
What an aspect ratio means
Aspect ratio describes shape, not sharpness. The same 16:9 frame can be 720p or 4K — megapixels change detail, not proportions.
Simplified W:H
Width and height divided by their greatest common divisor. 1920×1080 and 3840×2160 both reduce to 16:9 — the same shape at different pixel counts.
Decimal ratio
Width ÷ height. Useful in CSS and code: 16:9 ≈ 1.778, 21:9 ≈ 2.333, 9:16 ≈ 0.562. Portrait values are less than 1.
Megapixels vs shape
Megapixels equal (width × height) ÷ 1,000,000. Two panels can share a ratio and differ wildly in megapixels — density is a separate question (see PPI).
How to use the aspect ratio calculator
Three steps: enter dimensions, load a common ratio if needed, then resolve a missing side when you only know width or height.
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Enter width and height
Type pixel width and height in the Ratio Calculator card. Aspect ratio, decimal, megapixels, and the preview outline update instantly as you type. See also: resolution check guide .
Tip Use native pixels, not a cropped export size, when checking a panel
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Try common ratios
Pick a Common Ratios row (16:9 Standard Wide, 21:9 Ultrawide, 9:16 Portrait, and more) to load a matching pair. Use the Compare bar on the preview to overlay a second ratio in yellow. See also: common ratio reference .
Tip Marketed “21:9” panels are sometimes near-21:9 pixel grids
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Resolve the missing side
In Dimension Resolver, choose Known Width or Known Height, enter the known value, and copy the calculated side. Full Size shows width × height at the active ratio. See also: screen size calculator .
Tip Lock ratio first, then solve for the unknown side
Common ratios explained
16:9 (standard wide)
Default for TVs, most monitors, and YouTube. 1080p, 1440p, and 4K usually share this shape.
16:10 & 3:2
Taller than 16:9 — common on productivity laptops. More vertical workspace for documents and code.
21:9 & 32:9
Ultrawide and super-ultrawide. Great for timelines and multitasking; verify desk width before purchase.
9:16, 1:1, 4:3
Phone stories, social crops, and legacy content. Use the preview to confirm portrait vs square framing.
Aspect ratio needs by use case
Video & streaming
- Match timeline resolution to the delivery ratio (usually 16:9).
- Ultrawide sources may letterbox on 16:9 TVs.
- Solve height from a known width when exporting.
UI & design
- Confirm artboards match target device ratios before handoff.
- 9:16 and 1:1 crops fail if the source canvas is wrong.
- Use decimal ratios in CSS aspect-ratio properties.
Gaming & monitors
- 21:9 and 32:9 change FOV and HUD layout.
- Multi-monitor setups may combine different ratios.
- Check native panel ratio before buying a new display.
Phones & social
- Stories and Reels lean on 9:16.
- Square 1:1 still matters for some feeds.
- Preview orientation before cropping screenshots.
Aspect ratio calculator FAQs
How do I calculate aspect ratio from resolution?
Divide width and height by their greatest common divisor. For 2560×1440 that divisor is 160, so the ratio is 16:9. This calculator does that simplification automatically.
Can I find height if I only know width and ratio?
Yes. Open Dimension Resolver, select Known width, enter the width and target ratio (or set width/height fields first). Height is width × (ratio height ÷ ratio width).
Is 2560×1080 the same as 21:9?
Close, but not exact. 2560×1080 simplifies to 64:27 (~2.370), while true 21:9 is 2.333. Many “ultrawide” panels market 21:9 while shipping near-21:9 pixel grids.
Does this measure my physical monitor?
No — it converts numbers you enter. For physical size and PPI, use the Screen Size Calculator. For live OS resolution and DPR, use the Resolution Checker.
What is a decimal aspect ratio?
Decimal ratio is width ÷ height. 16:9 is about 1.778; 21:9 is about 2.333; 9:16 is about 0.562. It is handy for CSS and code that expect a single number.
How are megapixels calculated?
Megapixels equal (width × height) ÷ 1,000,000. They describe pixel count, not shape — two 16:9 images can have very different megapixel totals.
Aspect ratio calculator tips
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Native pixels first
Enter the panel or export’s true pixel size — scaled previews distort the ratio.
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Resolve one side
Lock Known width or Known height after picking a ratio when the other dimension is unknown.
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Check display mode
Windows “Scale and layout” changes UI size, not the panel’s native aspect ratio.
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Looks like ≠ ratio
macOS scaled modes change logical resolution; native panel ratio stays the same.
