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Compute missing width or height to keep any aspect ratio.
🔒 100% client-side. Enter a ratio and one dimension; the other is computed as dim = known × (target / source).
An aspect ratio is the proportional relationship between width and height (expressed as W:H, like 16:9). When you resize an image, video, or container, keeping the ratio constant prevents stretching and distortion. This calculator takes any ratio plus one dimension and computes the other — or fits a ratio into a bounding box.
Given a ratio W:H, the dimensions are always proportional: width ÷ height = W ÷ H. So if you know the width, height = width × (H ÷ W); if you know the height, width = height × (W ÷ H). For a 16:9 video at 1920px wide, the height is 1920 × (9 ÷ 16) = 1080. The calculator handles the division for any ratio, including odd ones like 5:4 or 21:9.
When fitting a ratio into a fixed box, contain scales the image so the whole thing is visible, possibly leaving letterbox bars. Cover scales so the box is completely filled, cropping the overflow. CSS object-fit and background-size use these same terms. Pick contain when you must show the entire image; pick cover when the box must stay full (e.g. hero backgrounds).
The Aspect Ratio Calculator lets you figure out aspect ratio calculatorinstantly, without reaching for a spreadsheet or doing the math by hand. Whether you're planning a budget, checking a loan, or working through homework, the tool applies the correct formula behind the scenes and shows the result the moment you enter your numbers.
Unlike a static chart or table, this calculator adapts to your exact inputs. You can adjust any value and see the outcome update in real time, which makes it easy to compare scenarios — for example, "what if the rate were 1% lower?" or "what if I paid an extra $50 a month?"
Common uses: people reach for this tool when they need to find a aspect ratio calculator resize image, 16 9 ratio dimensions calculator, calculate height from width and ratio, or video aspect ratio resizer.
Browser-based tools like this one have a few real advantages over installed software or manual methods:
The Aspect Ratio Calculator is based on the following formula:
h₂ = h₁ × ( w₂ / w₁ )
Variables: w₁: original width (px) h₁: original height (px) w₂: new width (px) h₂: new height (px)
Resize while keeping the aspect ratio: the height scales by the same factor as the width. Given one new dimension, the other is computed to preserve the proportion.
Worked example: Step 1: Original image is 1920 × 1080; new width is 1280. Step 2: Scale factor = 1280 / 1920 = 0.6667. Step 3: h₂ = 1080 × 0.6667 = 720. Result: 1280 × 720, the same 16:9 ratio.
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