3 min read

Source: Roblox Creator Hub · CC BY 4.0 · View source · Code samples: MIT Imported 2026-10-03. Formatting adapted for this site.

UDim

The UDim data type represents a one-dimensional value with two components: a relative scale and an absolute offset in logical pixels. At evaluation time, the engine computes the final pixel value as Scale * referenceMeasurement + Offset, where the reference measurement is typically the size of a parent GuiObject along the corresponding axis.

UDim values appear individually in properties such as UICorner.CornerRadius, UIPadding.PaddingTop, and UIStroke.Thickness, or paired as a UDim2 for two-dimensional sizing and positioning.

-- 50% of the parent plus 10 extra logical pixels
local dimension = UDim.new(0.5, 10)

Constructors

UDim.new

Returns a new UDim from the given Scale and Offset components. Both parameters are optional and default to 0 when omitted; calling UDim.new() with no arguments produces a UDim equivalent to UDim.new(0, 0).

local fullScale = UDim.new(1, 0)    -- 100% of parent, no pixel offset
local fixedPixels = UDim.new(0, 200) -- 0% scale, 200 pixel offset
local mixed = UDim.new(0.5, 20)      -- 50% of parent plus 20 pixels

Parameters

Properties

UDim.Scale

The relative scale component of the UDim, expressed as a fraction of a reference measurement (typically the corresponding axis of a parent GuiObject). A value of 1 represents the full reference measurement, 0.5 represents half, and 0 means the scale contributes nothing to the resolved pixel value. Defaults to 0 when not specified in the constructor. This property is read-only.

UDim.Offset

The absolute offset component of the UDim in pixels. This value is added to the resolved scale portion (Scale * referenceMeasurement) to produce the final pixel measurement. The offset is stored as an integer. Defaults to 0 when not specified in the constructor. This property is read-only.

Operators

UDim + UDim (addition)

Produces a UDim whose Scale is the sum of the two operands' scales and whose Offset is the sum of their offsets. Each component is added independently: UDim.new(a.Scale + b.Scale, a.Offset + b.Offset).

UDim - UDim (subtraction)

Produces a UDim whose Scale is the difference of the two operands' scales and whose Offset is the difference of their offsets. Each component is subtracted independently: UDim.new(a.Scale - b.Scale, a.Offset - b.Offset).