Manually setting measurments

Is there a way to select an object a manually enter the dimensions?

There probably is. Can you give a specific example of what you want to change the dimensions of?

Most Dynamic Components allow you to do that. And a few plugins draw geometry from given input parameters - 3D Parametric shapes from Sketchucation Plugin Store, which I adapted from an earlier Sketch up plugin, is one such.

And I’ve seen a parametric grid.

As DaveR says, what do you want to do?

But as far as I know, once you have changed to another tool, in native Sketchup you can’t do that for existing objects, just for something you haven’t yet finished drawing.

Some objects can be changed via the Entity Info panel. Such as circles, etc.

Of course, Dan -thanks for the reminder. I did know that, but forgot it in this context.

Another way is to use ‘Scale’.
If you select the object, and start a Scaling operation along a particular axis and type in a number + [enter] then it scales proportionally - so using 2.5 will make it 2.5 times bigger than it was…
However, if you include a units suffix it makes it that exact dimension - so 2.5" makes it 2.5 inches, whereas 2.5m makes it 2.5 meters etc…