About the PPI Calculator
Pixel density, in pixels per inch, tells you how sharp a screen is. A higher number means smaller pixels and finer detail. It depends on the resolution and on the physical size of the screen, so a large 4K monitor and a small 4K tablet have very different densities. This calculator takes the width and height in pixels and the diagonal in inches, and returns the PPI, the pixel size, the physical size and the aspect ratio. Type the width and height in pixels and the diagonal in inches and the pixel density appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the PPI Calculator
- 1Enter the width and height in pixels and the diagonal in inches.
- 2Pick the units or options from the menus if the pixel density tool offers them.
- 3Read the pixel density in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the pixel density
Designers use PPI to size interface elements, buyers use it to compare monitors, and photographers use it to know how large an image can look on a display. It also helps to explain why text looks crisp on a phone and rough on a large TV.
At a normal distance of 20 to 24 inches, around 100 PPI looks acceptable, and about 220 PPI looks sharp on a laptop. Phones, held closer, benefit from 400 PPI or more.
How the pixel density is worked out
PPI = √(width² + height²) ÷ diagonal. Pixel pitch = 25.4 mm ÷ PPI. A 24 inch full HD monitor (1,920 × 1,080) has 91.8 PPI, a pixel pitch of 0.277 mm and a screen of 20.9 × 11.8 inches. A 6.1 inch phone with 2,532 × 1,170 pixels has 457 PPI, about five times as dense.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- PPI, pitch and size
- Aspect ratio reduced
- Megapixels
Mistakes to avoid with pixel density
PPI is for screens, and DPI is for printers, although people mix the two. The advertised diagonal is rounded, so the PPI is only approximate. The aspect ratio shown is reduced exactly from the pixel counts, so it may look odd, such as 422:195, when the screen is not a standard shape.
On phone and computer
On a phone, type into the boxes one after another and read the pixel density underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the pixel density move. The ppi calculator works the same on both. Pixel density is one part of picking a screen or a print. Check sizes with the Screen Size Checker, work out the shape with the Aspect Ratio Calculator, and see how large a photo can print with the Print Size Calculator.
Features
- Diagonal is rounded
- PPI is for screens
- Higher PPI, finer detail
- Clear messages when the pixel density inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate pixel density?
PPI = √(width² + height²) ÷ diagonal. Pixel pitch = 25.4 mm ÷ PPI. A 24 inch full HD monitor (1,920 × 1,080) has 91.8 PPI, a pixel pitch of 0.277 mm and a screen of 20.9 × 11.8 inches. A 6.1 inch phone with 2,532 × 1,170 pixels has 457 PPI, about five times as dense.
What is the formula for pixel density?
PPI = √(width² + height²) ÷ diagonal. Pixel pitch = 25.4 mm ÷ PPI. The ppi calculator applies it exactly and rounds only the displayed answer to six significant figures.
What is a good PPI?
Around 100 for a desktop monitor at normal distance, 220 for a laptop and 400 or more for a phone.
Is PPI the same as DPI?
Not exactly. PPI counts pixels on a screen and DPI counts dots on paper.
Why does a 4K monitor look sharper at 27 inches than at 43?
The same number of pixels is spread over a larger area, so the PPI is lower.
Is this ppi calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.