Aspect Ratio Calculator
Find the matching height for a new width, and the simplified ratio.
Your figures
Result
How to use this tool
- Enter your own figures over the defaults — Width, Height, New width.
- The answer updates as you type. There is no button, and nothing is sent anywhere.
- Change Width on its own to see how much it moves the result — the worked example below shows exactly that.
Essential when resizing images or video without distortion. Also shows the megapixel count, which some upload forms limit.
How it works
This takes 3 inputs — width, height, new width — and returns matching height, aspect ratio, decimal ratio and megapixels. The whole calculation happens in this page as you type: there is no submit button, no request, and nothing stored.
Because it recalculates on every keystroke you can use it as a sensitivity test rather than a one-shot answer. Moving width alone from 1,920 to 2,112 changes matching height from 720 px to 655 px — the worked example below sets that out in full.
A worked example
Worked through with the figures the page already has in it: width of 1,920 px and height of 1,080 px, and the rest as shown, giving matching height of 720 px. These numbers come from running the calculator’s own code, not from being typed in here, so they cannot drift away from what you see on screen.
Starting from:
- Width: 1,920 px
- Height: 1,080 px
- New width: 1,280 px
| Result | Value |
|---|---|
| Matching height | 720 px |
| Aspect ratio | 16:9 |
| Decimal ratio | 1.7778 |
| Megapixels | 2.07 MP |
What happens when one input moves
Holding everything else steady and changing Width from 1,920 px to 2,112 px — 10% — moves the answer like this:
| Figure | 1,920 px | 2,112 px |
|---|---|---|
| Matching height | 720 px | 655 px |
| Aspect ratio | 16:9 | 88:45 |
| Decimal ratio | 1.7778 | 1.9556 |
| Megapixels | 2.07 MP | 2.28 MP |
That is usually the number worth arguing over: it is easier to move than the headline amount, and the difference compounds across the whole term.
Aspect Ratio Calculator — frequently asked questions
What is an aspect ratio?
The proportional relationship between width and height. 1920 × 1080 simplifies to 16:9.
Common video ratios?
16:9 for most video, 9:16 for vertical mobile, 4:5 for Instagram portrait, 1:1 for square, and 2.39:1 for cinematic widescreen.
Why does my image look stretched?
Because width and height were changed by different proportions. Use the matching height this calculator gives to keep the ratio intact.
Is this calculator free?
Yes, with no account, no limits and no data collection. It runs entirely in your browser.
Should I rely on this for a financial or medical decision?
No. It is a planning estimate built on standard formulas and stated assumptions. For decisions that matter, speak to a qualified professional who can account for your full circumstances.
How accurate is the Aspect Ratio figure?
The arithmetic is exact. With the defaults on this page — width 1920 px, height 1080 px, new width 1280 px — it returns matching height of 720 px. What limits accuracy is the assumptions, not the maths: change width to 2112 px and the same formula gives 655 px. Treat it as a well-founded estimate, not a quotation.
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Nothing is sent anywhere. The figures you type stay in this page and are never transmitted or stored — how that works.
Disclaimer. The formula is exact; the answer is only as good as the figures and assumptions above. Not financial, tax, medical or legal advice. Full disclaimer.