# PPI Calculator & Screen Size Comparison

> Free PPI calculator: pixel density, dot pitch, screen size, retina distance and OS scaling from any resolution, a to-scale screen size comparison and a TV viewing distance calculator.

Work out the pixel density (PPI) of any monitor, laptop, phone or TV from its resolution and diagonal, with dot pitch, physical size, aspect ratio, retina distance and the Windows scaling that suits it. Compare up to four screens drawn to scale, including ultrawides, and find the best viewing distance for a TV or the best TV size for your sofa.

- **Live tool:** https://www.toolnova.org/utilities/ppi-calculator
- **Category:** Calculators & Converters (https://www.toolnova.org/utilities)
- **Price:** Free
- **Requirements:** Runs in a modern web browser · No signup · No install

## What this tool does

- PPI and pixels per cm from any resolution and diagonal, with 30 presets for monitors, laptops, phones, tablets and TVs.
- Dot pitch, physical width, height and area, total megapixels and aspect ratio detection (including 21:9 and 32:9).
- Retina distance: how far away pixels become invisible to 20/20 vision.
- Suggested Windows/macOS scaling with the 'looks like' resolution.
- Sharpness bar comparing your screen with common monitors, laptops and phones.
- Screen size comparison for up to four screens drawn to scale, on a desk, centred or overlaid, with PPI per screen.
- Width, height and area differences in a table, plus PNG download of the drawing.
- Viewing distance calculator (SMPTE 30°, THX 40° and retina limit) and best TV size for your seat distance.
- Inches and feet or centimetres and metres; settings are remembered.

## How to use PPI Calculator & Screen Size Comparison

1. **Pick a preset or enter your screen** — Choose a monitor, laptop, phone or TV, or type the resolution in pixels and the diagonal in inches.
2. **Read the pixel density** — PPI, dot pitch, size, retina distance and the suggested scaling update instantly.
3. **Compare screens** — Open Size comparison, set each screen's diagonal, aspect ratio and resolution, and switch between desk, centred and overlay views.
4. **Find the viewing distance** — Open Viewing distance to get the best distance for a TV, or the best TV size for how far you sit.

## Common use cases

- Choosing between a 27-inch 1440p and 4K monitor
- Comparing a 34-inch ultrawide with a 27-inch or 32-inch 16:9 screen
- Finding how far to sit from a 55, 65 or 75-inch TV
- Choosing the right TV size for a living room
- Picking Windows display scaling for a 4K or high-DPI laptop
- Checking phone and tablet sharpness

## About

### How to calculate PPI

Pixels per inch is the diagonal resolution divided by the diagonal size: PPI = √(width² + height²) ÷ diagonal. A 27-inch 2560×1440 monitor has √(2560² + 1440²) = 2,937 pixels along its diagonal, so 2,937 ÷ 27 ≈ 109 PPI. Higher PPI means smaller pixels and sharper text at the same distance.

| Screen | Resolution | PPI | Retina from |
| --- | --- | --- | --- |
| 24" 1080p | 1920×1080 | 92 | about 37 in / 95 cm |
| 27" 1440p | 2560×1440 | 109 | about 32 in / 80 cm |
| 27" 4K | 3840×2160 | 163 | about 21 in / 54 cm |
| 32" 4K | 3840×2160 | 138 | about 25 in / 63 cm |
| 34" ultrawide | 3440×1440 | 110 | about 31 in / 79 cm |
| 65" 4K TV | 3840×2160 | 68 | about 4.2 ft / 1.3 m |

### What is a good PPI?

There's no single best number because it depends on how far away you sit. Desktop monitors at arm's length look fine from about 90 PPI, sharp from about 110 PPI and very crisp above 140 PPI. Laptops sit closer, so 150 to 220 PPI is common, and phones held 30 cm away use 400 PPI or more. Compare your screen's retina distance with your real viewing distance: if you sit farther away than the retina distance, extra pixels won't be visible.

| Device | Typical distance | Looks sharp from |
| --- | --- | --- |
| Desktop monitor | 60–80 cm | 110+ PPI |
| Laptop | 40–60 cm | 150+ PPI |
| Tablet | 35–45 cm | 250+ PPI |
| Phone | 25–35 cm | 400+ PPI |
| TV | 2–3 m | 40+ PPI |

### TV viewing distance and size

SMPTE recommends the screen fill at least 30° of your horizontal field of view for comfortable viewing, and THX recommends about 40° for a cinema-like picture. For a 16:9 TV that works out to roughly 1.6 times the diagonal (SMPTE) and 1.2 times the diagonal (THX). A 65-inch TV is best viewed from about 6.5 to 8.8 feet (2 to 2.7 m). The calculator also tells you whether 1080p, 4K or 8K keeps up at that size and distance.

| TV size | THX 40° | SMPTE 30° |
| --- | --- | --- |
| 43" | 4.3 ft / 1.3 m | 5.8 ft / 1.8 m |
| 55" | 5.5 ft / 1.7 m | 7.5 ft / 2.3 m |
| 65" | 6.5 ft / 2.0 m | 8.8 ft / 2.7 m |
| 75" | 7.5 ft / 2.3 m | 10.2 ft / 3.1 m |
| 85" | 8.5 ft / 2.6 m | 11.5 ft / 3.5 m |

### Comparing screens with different aspect ratios

Diagonal size hides a lot. A 34-inch 21:9 ultrawide is about the same height as a 27-inch 16:9 monitor but about a third wider, while a 32-inch 16:9 screen is taller than both. The comparison draws screens to scale on a desk, centred or overlaid from one corner, and lists the width, height and area difference so you know exactly what you're gaining.

See also: [Pixels to Inches Converter](https://www.toolnova.org/utilities/pixel-to-inches-calculator), [Refresh Rate Test](https://www.toolnova.org/diagnostics-tools/refresh-rate-test), [Dead Pixel Test](https://www.toolnova.org/diagnostics-tools/dead-pixel-test), [Monitor Ghosting Test](https://www.toolnova.org/diagnostics-tools/monitor-ghosting-test)

## FAQ

### How do I calculate pixels per inch?

Divide the diagonal resolution by the diagonal size: PPI = √(width² + height²) ÷ diagonal inches. Enter your resolution and size above and the calculator does it for you.

### What is a good PPI for a monitor?

Around 90 to 110 PPI is standard for desktop monitors at normal distance. 140 PPI and above looks very sharp, especially for text. Phones use 400 PPI or more because they're held close.

### Is 27-inch 1440p or 4K better?

27-inch 1440p is about 109 PPI; 27-inch 4K is about 163 PPI and looks noticeably sharper up close, but needs more GPU power for games and usually 150% scaling for comfortable text.

### Is a 34-inch ultrawide bigger than a 27-inch monitor?

It's about the same height as a 27-inch 16:9 screen but roughly a third wider. The comparison tab shows them to scale.

### How far should I sit from a 65-inch TV?

About 6.5 to 8.8 feet (2 to 2.7 m) using the THX 40° and SMPTE 30° guidelines. At that distance 4K looks fully sharp; 1080p shows visible pixels closer than about 8.4 feet.

### What scaling should I use on a 4K monitor?

On a 27-inch 4K monitor 150% keeps text about the same size as a 1440p screen, so it looks like 2560×1440. On a 32-inch 4K screen 125% is common. The calculator suggests a scaling level for any screen.

### What is dot pitch?

The distance between the centres of two adjacent pixels, usually in millimetres. It equals 25.4 ÷ PPI, so a 109 PPI monitor has a dot pitch of about 0.233 mm.

### What is retina distance?

The distance at which a person with 20/20 vision can no longer see individual pixels, because one pixel spans one arc-minute. It is about 3,438 ÷ PPI inches.

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