Calculating your pixels per inch (ppi) is straightforward once you know the Screen PPI formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Screen PPI Calculator.
What is Screen PPI?
The Screen PPI calculation tells you your pixels per inch (ppi) from a few simple inputs. The figure you are solving for here is the pixels per inch (ppi).
The Screen PPI formula
The core formula is:
Pixels per inch (PPI) = √(Horizontal resolution ^ 2 + Vertical resolution ^ 2) ÷ Screen diagonalHere is what each input means:
- Horizontal resolution — a value measured in px. Example: 1,920 px.
- Vertical resolution — a value measured in px. Example: 1,080 px.
- Screen diagonal — a value measured in in. Example: 15.6 in.
How to calculate it step by step
- Write down the horizontal resolution (for example, 1,920 px).
- Write down the vertical resolution (for example, 1,080 px).
- Write down the screen diagonal (for example, 15.6 in).
- Apply the formula above to get your pixels per inch (ppi).
- Double-check the result with the Screen PPI Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Horizontal resolution | 1,920 px |
| Vertical resolution | 1,080 px |
| Screen diagonal | 15.6 in |
| Pixels per inch (PPI) | 141.2 |
With horizontal resolution of 1,920 px, vertical resolution of 1,080 px and screen diagonal of 15.6 in, the pixels per inch (ppi) works out to 141.2.
Example 2
With horizontal resolution of 3,800 px, vertical resolution of 1,080 px and screen diagonal of 15.6 in, the pixels per inch (ppi) works out to 253.2.
| Result | Value |
|---|---|
| Pixels per inch (PPI) | 253.2 |
Example 3
With horizontal resolution of 960 px, vertical resolution of 1,080 px and screen diagonal of 15.6 in, the pixels per inch (ppi) works out to 92.6.
| Result | Value |
|---|---|
| Pixels per inch (PPI) | 92.6 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Screen PPI Calculator does it instantly, for free, with the formula and a worked example built in.
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