CSS Pixel to Device Pixel Calculator
Multiply each CSS dimension by device pixel ratio to obtain backing dimensions. An 800 × 600 CSS-pixel area at a ratio of 2 needs 1,600 × 1,200 device pixels.
Formula & method
Backing width = ceil(CSS width × DPR); backing height = ceil(CSS height × DPR).Worked example
| Input | Value |
|---|---|
| CSS width | 800 CSS px |
| CSS height | 600 CSS px |
| Device pixel ratio | 2 × |
| Result | Value |
|---|---|
| Rounded-up backing width | 1,600 px |
| Rounded-up backing height | 1,200 px |
| Total backing pixels | 1,920,000 |
Compare scenarios
The first input changes while the other example inputs stay fixed. These are arithmetic scenarios, not forecasts.
| Compare scenarios | CSS width CSS px | Rounded-up backing width | Rounded-up backing height | Total backing pixels |
|---|---|---|---|---|
| −20% | 640 | 1,280 px | 1,200 px | 1,536,000 |
| Example | 800 | 1,600 px | 1,200 px | 1,920,000 |
| +20% | 960 | 1,920 px | 1,200 px | 2,304,000 |
Assumptions & limits
Rounding each dimension up avoids allocating a fraction of a backing pixel. The device ratio is entered manually; this tool does not inspect the display. Browsers, zoom and image rendering choices can affect how a result is displayed.
Displayed results are rounded. Calculations use unrounded JavaScript numbers; small floating-point differences are possible.
Works in your browser
The interactive tool runs in a sandbox with network access blocked. ClearByte and the advertising scripts cannot read values inside it. Browser extensions and a compromised device remain outside this protection.
Sources & definitions
Method checked:
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