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Pixels per Inch Calculator

Calculate PPI/DPI. Free online Pixels per Inch Calculator. Calculate pixels per inch online — fast, accurate, mobile-friendly, no signup needed.

PPI
91.787799

Derivation

  1. ├── 01Givenw = 1920, h = 1080, diag = 24
  2. ├── 02Formula√(t²+a²) / n
  3. └── 03Compute PPI91.787799
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§01What is

Understanding the Pixels per Inch Calculator

The Pixels per Inch Calculator computes PPI from 3 inputs: width (px), height (px), diagonal (in). Calculate PPI/DPI.

Quick calculators for the math that shouldn’t need a notepad — instant, accurate, private to your browser. The Pixels per Inch Calculator sits in that toolkit — it calculate PPI/DPI. Enter your numbers above and the result updates instantly; every step of the math is shown in the Derivation panel so you can see exactly how the answer was reached.

§02The Formula

How it’s calculated

√(t²+a²) / n

Where

w
Width (px)
h
Height (px)
diag
Diagonal (in)
§03Practical Example

Step-by-step walkthrough

Scenario

Apply the formula to a realistic set of inputs: Width (px) = 1920, Height (px) = 1080, Diagonal (in) = 24.

  1. 01Start by noting the input — Width (px): 1920.
  2. 02Start by noting the input — Height (px): 1080.
  3. 03Start by noting the input — Diagonal (in): 24.
  4. 04Substitute these values into the formula: √(t²+a²) / n
  5. 05Compute PPI: the calculator returns 91.7878.
  6. 06Cross-check the answer by opening the Derivation panel above — every line of math is shown so you can follow the computation end-to-end.
§04Variants

Common Pixels per Inch Problems

The formula gets rearranged depending on which variable you need. Here are the patterns you’ll run into in the real world — find the one that matches your problem and follow the worked steps.

01 · PATTERN

Width (px) halved

w = 960 (from 1920)

Keep every other input at its default and halve the width (px). See how ppi responds.

  1. 01New Width (px): 960
  2. 02Baseline PPI: 91.7878
  3. 03New PPI: 60.208
  4. 04PPI decreases by 34.4% → use this sensitivity to plan for real-world variation.
02 · PATTERN

Width (px) doubled

w = 3840 (from 1920)

Keep every other input at its default and double the width (px). See how ppi responds.

  1. 01New Width (px): 3840
  2. 02Baseline PPI: 91.7878
  3. 03New PPI: 166.208
  4. 04PPI increases by 81.1% → use this sensitivity to plan for real-world variation.
03 · PATTERN

Height (px) halved

h = 540 (from 1080)

Keep every other input at its default and halve the height (px). See how ppi responds.

  1. 01New Height (px): 540
  2. 02Baseline PPI: 91.7878
  3. 03New PPI: 83.1039
  4. 04PPI decreases by 9.5% → use this sensitivity to plan for real-world variation.
04 · PATTERN

Height (px) doubled

h = 2160 (from 1080)

Keep every other input at its default and double the height (px). See how ppi responds.

  1. 01New Height (px): 2160
  2. 02Baseline PPI: 91.7878
  3. 03New PPI: 120.416
  4. 04PPI increases by 31.2% → use this sensitivity to plan for real-world variation.
§05FAQ

Frequently asked questions

Yes. The calculator implements the standard formula as documented and returns exact floating-point results. No approximations are used unless noted in the formula.
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