Why is there no 2.5x scale?

iOS defines exactly three scales: 1x, 2x, and 3x. Accepting a fractional scale here would invent a value that does not exist on the platform.

What is the difference between pt and px on an iPhone?

Points are the unit you design in. Pixels are what the screen has, so the same layout is three times as many pixels on a 3x device.

Does this account for Dynamic Type?

No. It converts the number you give it. If the user has scaled text up in Accessibility, the rendered height differs, and only the layout resolves that at runtime.

Why does Android need rounding and iOS not?

Android has density buckets at fractional scale factors such as 1.5x, so a dp can land on a half pixel. iOS scales are whole numbers, so the product is always a whole pixel.

pt to Pixel Converter

Convert iOS points to pixels at 1x, 2x, and 3x scale.

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pt to Pixel Converter on Loonix helps you convert iOS points to pixels at 1x, 2x, and 3x, the only three scales iOS actually has.

How to use

Enter the point value from your layout or design spec.
Pick the scale of the device you are targeting.
Read the pixel value, and note whether it comes out whole.

Features and limitations

Covers 1x, 2x, and 3x, the only scales iOS defines, and refuses fractional scales rather than rounding them.
Converts in both directions, so you can go from a screenshot back to the point value it was designed at.
Marks results that come out fractional, because a fractional px value is not valid in a layout literal.
Needs no rounding, which is the real difference from Android dp.

Limitation: Covers the three scales iOS defines. It does not account for Dynamic Type text scaling beyond the point value you enter, and it cannot tell you what Auto Layout will resolve for a given constraint.

Use cases

Convert a spec sheet written in points into the pixel values you need for assets.
Check whether a round point value lands on a whole pixel at each scale.
Reverse a retina screenshot back to the points its layout was designed at.

Frequently asked questions

Usage, result, and limitation information for this tool.

Why is there no 2.5x scale?: iOS defines exactly three scales: 1x, 2x, and 3x. Accepting a fractional scale here would invent a value that does not exist on the platform.
What is the difference between pt and px on an iPhone?: Points are the unit you design in. Pixels are what the screen has, so the same layout is three times as many pixels on a 3x device.
Does this account for Dynamic Type?: No. It converts the number you give it. If the user has scaled text up in Accessibility, the rendered height differs, and only the layout resolves that at runtime.
Why does Android need rounding and iOS not?: Android has density buckets at fractional scale factors such as 1.5x, so a dp can land on a half pixel. iOS scales are whole numbers, so the product is always a whole pixel.