Aspect Ratio Calculator
Find the simplified aspect ratio of any width and height, scale dimensions proportionally, or explore common screen and video ratios like 16:9, 4:3, and 1:1.
All calculations happen in your browser. No data is sent anywhere.
Find Aspect Ratio
Enter a width and height to get the simplified ratio, decimal value, and common name.
Results
| Simplified Ratio | — |
|---|---|
| Decimal Value | — |
| Common Name | — |
Scale Dimensions
Enter the original dimensions and supply either a new width or new height. The other value will be calculated to preserve the ratio.
Scaled Dimensions
| Scaled Width | — |
|---|---|
| Scaled Height | — |
Common Aspect Ratios
A reference table of widely used aspect ratios in video, photography, and social media.
| Ratio | Decimal | Name | Common Resolutions |
|---|---|---|---|
| 16:9 | 1.778 | Widescreen HD | 1920×1080, 1280×720, 3840×2160 |
| 4:3 | 1.333 | Standard / Old TV | 1024×768, 800×600, 640×480 |
| 1:1 | 1.000 | Square (Instagram) | 1080×1080, 720×720 |
| 21:9 | 2.333 | Ultrawide | 2560×1080, 3440×1440 |
| 3:2 | 1.500 | DSLR / 35mm Film | 3000×2000, 6000×4000 |
| 4:5 | 0.800 | Portrait (Instagram) | 1080×1350 |
| 9:16 | 0.563 | Mobile / Reels | 1080×1920, 720×1280 |
| 2:1 | 2.000 | Cinema / Cinerama | 2048×1024, 4096×2048 |
| 5:4 | 1.250 | Classic Monitor | 1280×1024, 2560×2048 |
| 3:4 | 0.750 | Old Tablet Portrait | 768×1024, 1536×2048 |
Understanding Aspect Ratios
Why 16:9 became the universal standard
The 16:9 ratio was selected as the HDTV standard in the 1980s as a geometric mean between the older 4:3 TV format and the wider 2.39:1 cinema format. It accommodates both without extreme letterboxing or pillarboxing. Today, virtually every smartphone, monitor, laptop, and streaming platform defaults to 16:9.
- 1920×1080 — Full HD, the most common broadcast and streaming resolution.
- 2560×1440 — QHD / 2K, popular for gaming monitors.
- 3840×2160 — 4K UHD, now standard on modern TVs and high-end displays.
Social media and content aspect ratios
Each platform has preferred ratios optimised for its feed layout. Using the wrong ratio can result in automatic cropping or black bars that reduce engagement.
- Instagram feed (landscape) — 1.91:1 (1080×566)
- Instagram feed (portrait) — 4:5 (1080×1350)
- Instagram / TikTok Reels — 9:16 (1080×1920)
- YouTube thumbnail — 16:9 (1280×720 minimum)
- Facebook / X (Twitter) post — 1.91:1 or 1:1
Video and cinema aspect ratios
The film industry has used a wide variety of ratios over the decades. Modern digital cinema often uses 2.39:1 (sometimes called 2.40:1 or "Scope"), while 1.85:1 is common for "flat" releases.
- 1.33:1 (4:3) — Early Hollywood and classic TV era.
- 1.85:1 — Standard widescreen cinema (flat).
- 2.39:1 — Anamorphic widescreen (scope), used in blockbusters.
- 2:1 — Used by Netflix originals and some streaming productions.
Photography and sensor crop factors
Camera sensors come in different native aspect ratios. Knowing your sensor's ratio helps you compose shots that won't need heavy cropping for a target output size.
- 3:2 — Full-frame and APS-C DSLRs and mirrorless cameras.
- 4:3 — Micro Four Thirds cameras and most phone cameras by default.
- 1:1 — Medium-format film, and phones in "square" mode.
- 16:9 — Video mode on most cameras and phones.
Related Tools
FAQ
What is an aspect ratio?
An aspect ratio describes the proportional relationship between the width and height of a rectangle, image, or screen. It is expressed as W:H (e.g. 16:9). A 16:9 display is 16 units wide for every 9 units tall, regardless of the physical size. Consistent aspect ratios ensure images and videos display without distortion across different screen sizes.
What does 16:9 mean?
16:9 means the width is 16 units for every 9 units of height. It is the standard widescreen format used by HD and 4K televisions, YouTube, and most modern monitors and laptops. Common resolutions include 1920×1080 (Full HD), 1280×720 (HD), and 3840×2160 (4K UHD). The ratio was standardised by the SMPTE as a practical middle ground between older TV and widescreen cinema formats.
How do I calculate an aspect ratio?
Divide both the width and height by their Greatest Common Divisor (GCD). For example, 1920×1080: GCD(1920, 1080) = 120, so 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9, giving 16:9. The decimal value is simply width divided by height (1920 ÷ 1080 ≈ 1.778). Use the Find Ratio tab above to do this instantly.
How do I scale dimensions while keeping the aspect ratio?
Enter the original width and height in the Scale Dimensions tab, then enter either the desired new width or new height (not both). The calculator applies the formula: new height = new width × (original height / original width), or new width = new height × (original width / original height). The result is rounded to the nearest whole pixel.
Is my data stored anywhere?
No. All calculations run entirely in your browser. Nothing is uploaded to any server.