Is dp (Density-independent Pixels) a Physical Size?

Question

According the definition of dp:

Density-independent Pixels - an abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi screen, so one dp is one pixel on a 160 dpi screen

We can calculate that 1dp = 1/160 inch, which is a physical size.

However dp seems not considered as a physical size like the table below,

this table is from answer of What is the difference between “px”, “dip”, “dp” and “sp”?

| Unit    | Description | Units Per     | Density     | Same Physical Size | 
|         |             | Physical Inch | Independent | On Every Screen    | 
+---------+-------------+---------------+-------------+--------------------+
| px      | Pixels      | Varies        | No          | No                 | 
+---------+-------------+---------------+-------------+--------------------+
| in      | Inches      | 1             | Yes         | Yes                | 
+---------+-------------+---------------+-------------+--------------------+
| mm      | Millimeters | 25.4          | Yes         | Yes                | 
+---------+-------------+---------------+-------------+--------------------+
| pt      | Points      | 72            | Yes         | Yes                | 
+---------+-------------+---------------+-------------+--------------------+
| dp      | Density     | ~160          | Yes         | No                 | 
|         | Independent |               |             |                    | 
|         | Pixels      |               |             |                    | 
+---------+-------------+---------------+-------------+--------------------+
| sp      | Scale       | ~160          | Yes         | No                 | 
|         | Independent |               |             |                    | 
|         | Pixels      |               |             |                    | 
+---------+-------------+---------------+-------------+--------------------+

So, yes or no.

If no, why? Thanks!

SteelToe SteelToe · Accepted Answer · 2019-04-17T02:36:31

Good Question!.

When they say physical size, they mean the physical number of pixels.

Since a high resolution screen has more pixels per inch then a low resolution screen. The physical number of pixels per dp will be less on the lower resolution screen.

That being said, most phone screens do not fit in perfectly into any bucket. What happens then is that android fits them into the closest bucket which can cause the number of pixel per dp to stray from the bucket amount.

Is dp (Density-independent Pixels) a Physical Size?

1 Answers