Enter width.
e.g. 1920
Enter height.
e.g. 1080
16:9
Enter width.
Enter ratio W.
Enter ratio H.
Enter height.
Enter ratio W.
Enter ratio H.
Enter width.
Enter height.
Leave blank to use target height
Leave blank to use target width
Aspect Ratio
—
Was this calculator helpful?
Sources & Methodology
Aspect ratio calculation uses the Euclidean GCD algorithm, consistent with IEEE and W3C standards for dimension ratios.
W3C CSS Sizing Level 4 — Aspect Ratio
W3C standard defining aspect ratio for CSS and web layouts, used as reference for ratio representation and scaling methodology
SMPTE Standards — Video Aspect Ratios
Society of Motion Picture and Television Engineers standards for 16:9, 4:3, and other broadcast aspect ratios
Methodology: GCD computed via Euclidean algorithm: gcd(a,b) = gcd(b, a mod b). Ratio = (W/GCD) : (H/GCD). Height from width: H = W × (rH/rW). Width from height: W = H × (rW/rH). Scale: factor = target/original; new dimension = other original × factor. Decimal ratio = W/H rounded to 4 decimal places.
⏱ Last reviewed: April 2026
How to Calculate Aspect Ratio
Aspect ratio expresses the proportional relationship between width and height as W:H. It describes shape without specifying actual size — a 1920×1080 monitor and a 640×360 thumbnail are both 16:9. Understanding aspect ratios is essential for video production, web design, photography, and responsive layouts.
The Aspect Ratio Formula
Ratio = (W ÷ GCD) : (H ÷ GCD)
GCD = Greatest Common Divisor of width and height (Euclidean algorithm)
Example: 1920 × 1080
GCD(1920, 1080) = 120
1920 ÷ 120 = 16 | 1080 ÷ 120 = 9
Aspect Ratio = 16:9 | Decimal = 1920/1080 = 1.778
Example: 1920 × 1080
GCD(1920, 1080) = 120
1920 ÷ 120 = 16 | 1080 ÷ 120 = 9
Aspect Ratio = 16:9 | Decimal = 1920/1080 = 1.778
Common Aspect Ratios Reference Table
| Ratio | Decimal | Common Resolutions | Used for |
|---|---|---|---|
| 16:9 | 1.778 | 1280×720, 1920×1080, 3840×2160 | HD/4K TV, YouTube, monitors |
| 4:3 | 1.333 | 640×480, 800×600, 1024×768 | Old TV, older monitors |
| 1:1 | 1.000 | 1080×1080, 500×500 | Instagram square, profile pics |
| 21:9 | 2.333 | 2560×1080, 3440×1440 | Ultrawide monitors, cinema |
| 9:16 | 0.5625 | 1080×1920 | Vertical video, Stories, Reels |
| 3:2 | 1.500 | 1500×1000, 3000×2000 | DSLR cameras, 35mm film |
| 2:1 | 2.000 | 2048×1024 | Panoramic photography |
Scaling While Maintaining Aspect Ratio
Scale Factor = Target Width / Original Width
New Height = Original Height × Scale Factor
Example: Scale 1920×1080 to width 960
Scale Factor = 960 / 1920 = 0.5
New Height = 1080 × 0.5 = 540
Result: 960×540 (same 16:9 ratio)
Example: Scale 1920×1080 to width 960
Scale Factor = 960 / 1920 = 0.5
New Height = 1080 × 0.5 = 540
Result: 960×540 (same 16:9 ratio)
💡 Quick check: Two sizes have the same aspect ratio if Width1 × Height2 = Width2 × Height1. Example: 1920×1080 and 1280×720 — check: 1920 × 720 = 1,382,400 and 1280 × 1080 = 1,382,400. Equal. Same 16:9 ratio confirmed.
Frequently Asked Questions
Aspect ratio is the proportional relationship between width and height, written W:H. It describes shape without size. 1920×1080 and 640×360 are both 16:9. The ratio tells you that for every 16 units of width there are 9 units of height.
Divide both dimensions by their Greatest Common Divisor (GCD). Example: 1920×1080. GCD=120. 1920/120=16, 1080/120=9. Aspect ratio=16:9. Decimal ratio=1920/1080=1.778.
16:9 is the widescreen standard for HD/4K TV, YouTube, and modern monitors. Common resolutions: 1280×720 (HD Ready), 1920×1080 (Full HD), 2560×1440 (QHD), 3840×2160 (4K UHD).
Height = Width × (Ratio H / Ratio W). Example: width=1280, ratio=16:9. Height=1280 × (9/16)=720. Result: 1280×720.
Width = Height × (Ratio W / Ratio H). Example: height=1080, ratio=16:9. Width=1080 × (16/9)=1920. Result: 1920×1080.
4:3 is the traditional SD television and older monitor format. For every 4 units of width there are 3 units of height. Common resolutions: 640×480, 800×600, 1024×768.
Multiply both dimensions by the same scale factor. To scale 1920×1080 to width 960: scale=960/1920=0.5. New height=1080×0.5=540. Result: 960×540, same 16:9 ratio.
1920×1080 has aspect ratio 16:9. GCD(1920,1080)=120. 1920/120=16, 1080/120=9. Decimal: 1.7778:1. This is the Full HD standard used in virtually all modern screens.
1:1 is a perfect square — width equals height. Used for Instagram square posts, profile photos, icons, and album art. Common sizes: 1080×1080, 500×500, 2000×2000.
9:16 is the portrait (vertical) format — the inverse of 16:9. Used for smartphone screens, Instagram Stories, TikTok, YouTube Shorts, and Reels. Standard resolution: 1080×1920.
Use width:100%;height:auto on img elements. For other elements, use the aspect-ratio CSS property: .box { aspect-ratio: 16 / 9; }. This tells the browser to maintain the 16:9 ratio as width changes.
16:9 is YouTube's standard. Upload at 1920×1080 (Full HD), 2560×1440, or 3840×2160 (4K) for best quality. YouTube Shorts use 9:16 (vertical). Non-16:9 videos get letterboxed or pillarboxed.
Ratio = (W/GCD):(H/GCD). Height from width: H=W×(rH/rW). Width from height: W=H×(rW/rH). Scale factor=Target/Original. Decimal ratio=W/H. All four operations are available in the tabs above.
Related Calculators
Popular Calculators
Stripe Fee Calculator
Finance
Pain & Suffering Calculator
Legal
TDEE Calculator
Health
Roofing Calculator
Construction
GPA Calculator
Education
Mortgage Refinance
Finance
CPM Calculator
Marketing
Markup Calculator
Finance
Adding And Subtracting Integers Calculator
Math
Average Time Calculator
Math
Hex To Octal Converter
Math
Hexagon Calculator
Math