How this calculator works
A 4:3 frame has four units of width for every three units of height, which is the same as 1.3333 when width is divided by height. The shape comes from early film and television and was carried into computer displays: VGA, SVGA, XGA and UXGA are all 4:3. When a 4:3 picture is shown on a widescreen 16:9 display, the player either adds black bars at the sides, called pillarboxing, or stretches and distorts the picture. Because every resolution in the table is exactly 4:3, one known side fixes the other: the height is three quarters of the width.
Formula
height = width x 3 / 4. width = height x 4 / 3. The decimal ratio is 4 / 3 = 1.333333. total pixels = width x height. megapixels = total pixels / 1,000,000.
Worked example
An XGA monitor is 1024 by 768 pixels. From the 1024 width, the height is 1024 x 3 / 4 = 768. The frame holds 786,432 pixels, or 0.786 megapixels. A 1600 by 1200 UXGA screen has 1,920,000 pixels, or 1.92 megapixels. If you need a 4:3 image that is 1200 pixels tall, the width is 1200 x 4 / 3 = 1600 pixels.
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Frequently asked questions
Is 4:3 the same as 1.33:1?
Yes for practical purposes. One and a third is 1.3333, and the small difference from 1.33 is below the precision of display specifications. The exact reduced ratio is 4:3.
Why do old television shows have black bars on a modern TV?
The show was recorded in 4:3, and a 16:9 screen is wider than the picture. Filling the screen would either stretch the image or crop the top and bottom, so most players show the whole frame with bars at the sides.
What is the difference between 4:3 and 3:2?
3:2 is slightly wider, with a decimal ratio of 1.5 instead of 1.3333. It is the shape of 35 mm film and many digital camera sensors, while 4:3 remains common in compact cameras and older video.
Can I print a 4:3 image without cropping?
Only on paper with the same proportions. A 4 by 6 inch print is 2:3, so a 4:3 photo must be cropped or given white borders to fit. Print sizes such as 4 by 5.33 inches keep the full 4:3 frame.