4:3 Aspect Ratio Calculator

A 4:3 frame is four units wide for every three units tall, a decimal value of about 1.333. It is a noticeably squarer rectangle than 16:9, which is why older television footage looks boxy next to a modern broadcast.

The ratio came from early film stock and was carried into cathode-ray televisions because the first picture tubes were built to match it. Computer monitors inherited the same shape, and for roughly fifty years the great majority of screens were 4:3. The shift to 16:9 in the 2000s was driven by widescreen film and by the desire to show letterboxed movies without wasting tube space, not by any change in how people use screens.

Reducing a 4:3 resolution to its simplest form is quick, because VGA-derived sizes share large common factors: 1600 and 1200 reduce by 400, while 640 and 480 reduce by 160.

1. Divide the width by 4.
2. Multiply that result by 3 to get the matching height.
3. If the width does not divide evenly by 4, divide by 3 instead and multiply by 4 to get the width from a known height.

Worked example

From 1600 pixels wide: 1600 ÷ 4 = 400, and 400 × 3 = 1200, so the matching size is 1600 × 1200. For a 640-pixel width, 640 ÷ 4 = 160 and 160 × 3 = 480, giving the classic 640 × 480. The iPhone camera works the same way in reverse: a 4032 × 3024 photo is 4:3 because 4032 ÷ 4 = 1008 and 1008 × 3 = 3024.

People often assume every "old" photo or classic TV clip is exactly 4:3, but sensor and format variations mean some legacy footage is closer to 1.33 without landing on it precisely. The more damaging mistake is stretching 4:3 footage to fill a 16:9 frame instead of pillarboxing (adding side bars) or cropping — stretching distorts every face and object in the shot, making people look wider and shorter than they actually are.

For a 4:3 frame at 1024 pixels wide: 1024 ÷ 4 = 256, then 256 × 3 = 768. That gives 1024 × 768 — XGA, the standard legacy monitor and classroom-projector resolution, and an exact 4:3 frame.

Type your own numbers into the 4:3 calculator above and it will show the same division, plus the reduced ratio and the CSS to copy.

• iPad and Android tablet screens, several of which remain close to 4:3.
• Micro Four Thirds and many compact cameras, whose native sensor output is 4:3.
• PowerPoint decks set to the older 10 × 7.5 inch slide size.
• Scanned pages, forms and PDF renders that keep the original document proportions.
• Retro game emulation and pixel art, where the source material was authored in 4:3.
• Educational and archival video that has not been re-framed for widescreen.

4:3 sits between the square 1:1 frame and the widescreen 3:2 frame. The 3:2 calculator covers the ratio used by most DSLR and mirrorless cameras, while the 1:1 calculator covers square output for social feeds.

• 16:9
• 9:16
• 1:1
• 16:10
• 21:9
• 3:2
• 4:5
• 2:3
• 2.39:1

This 4:3 guide is one of ten ratio calculators on the site — the common aspect ratios table lists the decimal value and the typical uses for every one of them.

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  <iframe id="aspectcalc-frame" src="https://aspectcalc.com/embed?h=640"
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          loading="lazy" title="AspectCalc aspect ratio calculator"></iframe>
  <p style="margin:8px 0 0;font:13px/1.4 system-ui,sans-serif;color:#64748b;text-align:center">Powered by <a href="https://aspectcalc.com/" style="color:#2563eb;text-decoration:none">AspectCalc</a> - free aspect ratio calculator</p>
</div>
<script>
  // Optional: grow the frame to the widget's real height.
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The frame starts at a fixed height, so your layout never jumps. Resize it with ?h= - for example https://aspectcalc.com/embed?h=520 - or keep the small script in the snippet and the frame will follow the widget's real height instead.