There may be more elegant ways to do this, but the first thing that popped into my head was the fact that when you use Create > New Primitive, the Dialog that opens lets you choose the Size in Inches, Feet, Yards, Centimeters and Meters...
If you make a Plane Primitive (Z Positive might be the most useful Primary Axis) at 100 Inches, once it's in the Scene you could alter the X or Y Scale of the Primitive in the Parameter Tab and the % should pretty much reflect how many inches if whole numbers are used for the Scale, for instance 72% would be 72 Inches/6 Feet, etc.
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One option is the Measure Metrics product.
There may be more elegant ways to do this, but the first thing that popped into my head was the fact that when you use Create > New Primitive, the Dialog that opens lets you choose the Size in Inches, Feet, Yards, Centimeters and Meters...
If you make a Plane Primitive (Z Positive might be the most useful Primary Axis) at 100 Inches, once it's in the Scene you could alter the X or Y Scale of the Primitive in the Parameter Tab and the % should pretty much reflect how many inches if whole numbers are used for the Scale, for instance 72% would be 72 Inches/6 Feet, etc.
Make primitive cylinders of various legths to use as metering rods.
For a globe, make spheres of different diameters.Experiment until you make one that fits perfectly inside the globe you want to measure.
Props like this work great.
MWall 2.0 for Daz Studio by SpyroRue on DeviantArt
For measuring using primitives make the primitive one meter and adjust scale til it fit the object being measured then do the math.
This is my go-to: https://sharecg.com/v/40765/browse/11/Poser/Poser-height-measuring-rulers
Yes, it says "Poser", but it is indeed scaled right for Daz.
It also helps when using such rulers to use a non-perspective view like Front View.