What Is the 4:3 Aspect Ratio?

By Aspect Ratio Calculator Pro Editorial Team · Updated Oct 30, 2026

A 4:3 picture is four units wide for every three units tall. It was the shape of standard-definition television and, give or take a little, of films before the widescreen era, and it is still used on some tablets and cameras. This guide lists every common 4:3 resolution with exact pixel counts, compares 4:3 with 16:9 at the same diagonal, and shows how to convert between the two without stretching.

What does 4:3 mean?

An aspect ratio is width divided by height. For 4:3, that is 4 ÷ 3 = 1.333..., so the same shape is often written 1.33:1 (film books and archives prefer this form because it puts every ratio over a height of 1). 16:9 works out to 1.78:1, so a 4:3 frame is noticeably squarer.

A resolution is 4:3 when its height is exactly three quarters of its width. Check it with either test:

• Divide: width ÷ height = 1.3333. Example: 1024 ÷ 768 = 1.3333.
• Multiply: width × 3 ÷ 4 = height. Example: 1600 × 3 ÷ 4 = 1200.

To find the 4:3 height for any width, or check an odd size, use the Aspect Ratio Calculator.

What are the common 4:3 resolutions?

Every size below passes the exact test (width × 3 ÷ 4 = height, no rounding). Megapixels are total pixels divided by 1,000,000, rounded to two decimals.

Two rows matter most for video work. 1440 × 1080 is the largest 4:3 picture that fits in a 1920 × 1080 frame, and 2880 × 2160 is the largest that fits in a 3840 × 2160 (4K UHD) frame. Each is exactly 75% of the frame's width.

Sizes that look 4:3 but are not

Where did 4:3 come from?

Film came first. The National Film and Sound Archive of Australia's short history of aspect ratio says the ratio was fixed at 4×3 (1.33:1) in the silent era. When sound arrived, the frame was reduced to make room for a soundtrack, and that shape became the Academy ratio of 1.37:1, used for the majority of films made between the 1930s and 1950s. The same page describes Academy as roughly 4×3 and says television kept the 4×3 shape when it was introduced.

So 1.33:1 and 1.37:1 are two different film formats. The Academy ratio is about 3% wider (1.37 ÷ 1.333 = 1.03). On a 4:3 TV or monitor the difference shows up as thin bars, or as a tiny crop.

4:3 in standard-definition television

Digital SD television is defined in ITU-R BT.601, whose full title is "Studio encoding parameters of digital television for standard 4:3 and wide screen 16:9 aspect ratios." The title itself labels 4:3 as the standard shape and 16:9 as the wide one. BT.601 covers 525-line and 625-line systems, uses a 13.5 MHz sampling rate for both 4:3 and 16:9 images, and gives each digital active line 720 luminance samples whatever the picture shape.

That last detail is why SD video files confuse people. The same 720-sample line carries either a 4:3 or a 16:9 picture, so SD pixels are not square, and the stored pixel grid does not tell you the shape on screen. HDTV dropped that complication: ITU-R BT.709 defines a 1920 × 1080 picture with square pixels and a 16:9 shape. Our 1080p resolution guide covers that format.

Where is 4:3 used today?

Tablets. Apple's 13-inch iPads are the clearest example. Apple's iPad Pro specs list the 13-inch model at 2752 × 2064 pixels, which is exactly 4:3 (both numbers divide by 688, leaving 4 and 3). The 13-inch model on the iPad Air specs page is 2732 × 2048, which reduces to 683:512, or 1.3340:1, within 0.05% of 4:3. The smaller models are wider, so do not assume every iPad is 4:3:

The 11-inch figures come from the iPad 11-inch (A16) specs and the iPad Pro page.

Cameras. Micro Four Thirds cameras use a 4:3 sensor. OM SYSTEM's OM-1 Mark II specifications list the sensor's aspect ratio and area as 4:3 and 17.3 × 13.0 mm and the largest RAW and JPEG image size as 5184 × 3888 pixels, which is exactly 4:3 (20.16 megapixels). The same spec list also offers 3:2, 16:9, 6:6 and 3:4 aspect ratio settings. The system's name refers to the sensor size, not the shape: the Micro Four Thirds FAQ explains that the standard uses a 4/3-type image sensor, a size class that is twice the size of the 2/3-type sensors found in compact cameras.

Images for the web. Many social platforms crop to their own shapes, so a 4:3 photo may be trimmed in feeds. Check each platform's current frame sizes in our social media image sizes guide before you export.

4:3 vs. 16:9: which is bigger?

At the same diagonal, 4:3 is bigger. Screen sizes are sold by the diagonal, and a squarer rectangle encloses more area along the same diagonal.

The math, for a diagonal d:

• A 4:3 rectangle is a 3-4-5 triangle doubled, so its width is 0.8d and its height is 0.6d. Area = 0.48d².
• A 16:9 rectangle has a diagonal of √(16² + 9²) = √337 ≈ 18.358 units, so its width is 16d/√337 ≈ 0.8716d and its height is 9d/√337 ≈ 0.4903d. Area = 144d²/337 ≈ 0.4273d².
• Divide the two: 0.48 ÷ (144/337) = 337/300 = 1.1233.

A 4:3 screen has 12.33% more area than a 16:9 screen with the same diagonal. Put the other way, the 16:9 screen has 10.98% less area. It is 8.9% wider but 18.3% shorter.

Same-diagonal comparison table

Width, height and area in inches, computed from the formulas above and rounded to one or two decimals.

Two rules of thumb follow from the same numbers:

• Matching height: a 16:9 screen needs a diagonal 1.224 times larger to be as tall as a 4:3 screen. A 21-inch 4:3 monitor is 12.6 inches tall; a 16:9 screen needs a 25.7-inch diagonal to match.
• Matching area: a 16:9 screen needs a diagonal 1.060 times larger (the square root of 337/300). The 21-inch 4:3 monitor has the same area as a 22.3-inch 16:9 screen.

To turn these physical sizes into pixels at a given density, use Inches to Pixels.

Which should you use?

Use 16:9 for anything that will play on a TV, a monitor or a video platform, since HD and UHD video are 16:9. Use 4:3 when the destination is 4:3 (a 13-inch iPad, a Micro Four Thirds camera's full sensor, archival SD footage) or when you want a taller frame and can accept bars on wide screens.

How do you convert 4:3 to 16:9?

You have three choices. Only two keep the picture's proportions.

1. Pillarbox (fit): scale the 4:3 picture until it is as tall as the 16:9 frame, then fill the sides with bars. Nothing is cut off; the picture uses 75% of the frame width.
2. Crop (fill): keep the full width and cut the top and bottom until the shape is 16:9. The frame is filled, but 25% of the original height is lost, 12.5% from each edge if centered.
3. Stretch: scale the width by 1.333 without changing height. This fills the frame but makes everything 33% too wide. Avoid it.

4:3 to 16:9: exact pixel numbers

For a 4K UHD timeline (3840 × 2160), a pillarboxed 4:3 picture is 2880 × 2160 with 480-pixel bars on each side. Note that cropping small sources such as 640 × 480 and then scaling to 1080p means a 3× enlargement, which will look soft; pillarboxing keeps the original detail.

16:9 to 4:3

The reverse works the same way:

• Letterbox: 1920 × 1080 scaled into a 1024 × 768 frame becomes 1024 × 576 with 96-pixel bars top and bottom. Into 1600 × 1200 it becomes 1600 × 900 with 150-pixel bars.
• Crop: cut 1920 × 1080 down to 1440 × 1080 by removing 240 columns from each side. You keep 75% of the width.

Common 4:3 mistakes

1. Treating 1280 × 1024 as 4:3. It is 5:4. The 4:3 size at that width is 1280 × 960.
2. Calling the Academy ratio 4:3. Academy is 1.37:1, a little wider than 4:3's 1.33:1.
3. Reading the shape from an SD file's pixel grid. BT.601 uses 720 samples per line for both 4:3 and 16:9, so check the display aspect flag, not the stored width and height.
4. Assuming "Four Thirds" names the shape. The name refers to the 4/3-type sensor size, though the sensor is also 4:3.
5. Stretching to fill. A 4:3 picture stretched to 16:9 is 33% too wide. Pillarbox or crop instead.
6. Guessing image sizes. Before cropping a photo or screenshot, read its true pixel size with the Image Resolution Checker.

How this guide was made: an AI tool helped with research and the first draft, and we then checked each figure against the sources above. Found an error? Email editorial@aspectratiocalculatorpro.com. Editorial policy.

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