What Is the 4:3 Aspect Ratio?
An aspect ratio describes the proportional relationship between the width and height of a rectangular image, screen, or frame. A 4:3 aspect ratio means the width is four units and the height is three units. This produces a nearly square shape that was once the dominant standard for television and computer displays.
The ratio is also expressed as the decimal 1.333 (repeating), or written as 4/3. It is sometimes called "full frame" or "standard" to distinguish it from widescreen formats such as 16:9 or 16:10.
The Formula
The two formulas for working with the 4:3 ratio are straightforward:
- Height from width: height = width × 3 ÷ 4 (or width × 0.75)
- Width from height: width = height × 4 ÷ 3 (or height × 1.3333)
- Diagonal: diagonal = √(width² + height²) using the Pythagorean theorem
For example, if you know the width is 1,024 pixels, the height is 1,024 x 0.75 = 768 pixels. The diagonal is √(1,024² + 768²) = √(1,048,576 + 589,824) = √1,638,400 = 1,280 pixels.
Worked Example
Using the default inputs (width = 1,024 px):
- Height = 1,024 × 3/4 = 768 px
- Diagonal = √(1,024² + 768²) = √1,638,400 = 1,280.0 px
- Total pixel area = 1,024 × 768 = 786,432 px² (786K)
These match the calculator output for 1024 x 768, the XGA standard.
Common 4:3 Resolutions and Uses
| Resolution | Name | Common Use |
|---|
| 640 x 480 | VGA | Early PC monitors, DVD menus, retro gaming |
| 800 x 600 | SVGA | Standard PC monitors (1990s to early 2000s) |
| 1024 x 768 | XGA | Laptop screens, projectors, older tablets |
| 1280 x 960 | SXGA (variant) | Higher-res 4:3 desktops and projectors |
| 1400 x 1050 | SXGA+ | High-res 4:3 laptops and monitors |
| 1600 x 1200 | UXGA | High-end CRT monitors, professional photography |
| 2048 x 1536 | QXGA | iPad Retina (original), high-res scanning |
When Is 4:3 Used Today?
While 16:9 has replaced 4:3 for most consumer televisions and monitors, 4:3 remains common in several areas:
- Photography: Micro Four Thirds (MFT) cameras use a 4:3 sensor, which is a native 4:3 ratio. Many compact cameras also default to 4:3.
- Projectors: Older business projectors and some classroom projectors output in 4:3, so slideshow presentations often use 4:3 layouts.
- Print: Standard print sizes such as 4 inches x 3 inches (or scaled equivalents) follow this ratio, making it useful in desktop publishing.
- Gaming: Some competitive gamers prefer 4:3 stretched or native resolutions on modern hardware for gameplay reasons.
- Legacy video: PAL analogue television (as used in New Zealand until the switch-off in 2013) was broadcast in 4:3. Archiving or converting this content often requires working in 4:3 dimensions.
4:3 vs 16:9
The 16:9 ratio (decimal 1.778) is wider and shorter relative to its width than 4:3 (decimal 1.333). When displaying 4:3 content on a 16:9 screen, black bars appear on the left and right sides (called "pillarboxing"). Conversely, when a 16:9 image is displayed on a 4:3 screen, black bars appear at the top and bottom ("letterboxing"). To avoid bars, some devices stretch the image, which distorts the proportions.
Related Calculators
Method: Standard aspect ratio arithmetic: height = width x 3/4; width = height x 4/3; diagonal = √(width² + height²) via the Pythagorean theorem. No rounding is applied until display.
This calculator applies the exact 4:3 ratio formula. Results are correct for any unit of measurement (pixels, centimetres, inches, etc.) as long as you use the same unit for both dimensions. Diagonal results assume a flat rectangular geometry.
