Creating dimensions involves two basic steps: selecting the objects to be measured, and locating the dimension. By default the magnitude of the dimension is calculated automatically and is recorded as the dimension text, measured in current World units. (Leader dimensions, which contain text labels, are the exception to this rule.)You can override the default text of a dimension by specifying the text in the Inspector Bar prior to finishing the dimension. 
You can also change the dimension text in the dimension's Properties, by changing the Attributes field of the General page.
Note: To create several types of dimensions automatically in one step, see Auto Dimension.
When Auto Add Constraints is active, any dimensions you assign are created as variables that appear in the Calculator Palette. 
Dimension variables can be constrained to other dimensions, or to other variables or numbers. This is particularly powerful when used in conjunction with Auto Constraints. See Constraining Dimensions.
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Orthogonal Dimension
Anchor
Creates a horizontal or vertical dimension.
Note: To create orthogonal dimensions automatically, see Auto Dimension.
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Local menu options: Segment Dimensioning, Entity Dimensioning: See Segment and Entity Dimensioning. Horizontal / Vertical Mode only: creates either type of dimension, no matter where the dimension is located.
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Parallel Dimension
Creates a dimension showing the absolute length of an object.
Note: To create parallel dimensions automatically, see Auto Dimension.
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Local menu options: Segment Dimensioning, Entity Dimensioning: See Segment and Entity Dimensioning.
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Distance Dimension
Sets two lines parallel to one another and places a constrained dimension between them. For this tool to be available, Auto Add Constraints must be on. 
Note: To create distance dimensions automatically, see Auto Dimension.
- Select the two lines, or select them by snapping to either of their endpoints.
- Place the dimension, and the lines are made parallel.
Note: Because Auto Add Constraints is on, the Distance dimension appears as a variable in the Calculator Palette and can be edited. See Constraining Dimensions.
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Rotated Dimension
Creates a dimension projected in a specified direction.
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Local menu options: Segment Dimensioning, Entity Dimensioning: Available only after the dimension direction has been defined. See Segment and Entity Dimensioning.
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Datum Dimension
Creates a dimension showing the horizontal or vertical distance from a point. By default, the point is the absolute origin, but you can change this.
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Local menu options: Set Origin: By default, datum dimensions are created relative to the absolute origin. Use Set Origin to select a new origin. This origin will remain in effect until changed.
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Baseline Dimension
Creates a series of parallel linear dimensions that follow the axis of an existing linear dimension.
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Local menu option: Select Dimension: Select a new base dimension.
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Continuous Dimension
Creates a series of parallel linear dimensions measured from the previous dimension. The dimensions follow the axis of the base dimension.
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Local menu option: Select Dimension: Select a new base dimension.
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Incremental Dimension
Creates a series of parallel linear dimensions measured from the previous dimension. The dimensions follow the axis of the base dimension, and are displayed normal to the axis.
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Local menu option: Select Dimension: Select a new base dimension.
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Angular Dimension
Creates dimensions measuring angles. You can dimension the angle between two lines, the angle of an arc, between two points of a circle, and between a node and two points.
Note: To create angular dimensions automatically, see Auto Dimension.
Angle Between Two Lines
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- Select the angle vertex.
- Select two points defining the angle.
- Move the mouse to dimension the acute or obtuse angle. Click to locate the dimension, or enter the length and angle in the Inspector Bar.
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Radius - Diameter Dimension
Dimensions the radius or diameter of an arc or circle.
Note: To create radius or diameter dimensions automatically, see Auto Dimension.
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Local menu option: Large Radius: If the arc center is out of your drawing space, use this option to display the dimension from outside. 
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Leader
Creates dimension text attached to a simple line leader pointing to a location in your drawing. The leader is similar to a polyline.
Note: Check Draw as Spline on the Advanced Format page of the Properties window to create a curves leader rather than line segments.
- Enter the text in the Inspector Bar.
- Select the leader start point (the end with the arrow). Select or more additional segment endpoints, or enter the length and angle of each segment in the Inspector Bar.Note: The arrowhead is defined by Arrowheads / 1st on the Format page of the Properties window.
- Double-click to finish, or select Finish from the local menu, or press Alt+F.
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Wall Dimensions
There is a special tool for dimensioning walls created via the Architecture tools. See Wall Dimension.