I'm specifically talking about the Measure tool with the protractor icon. I wanted to resize my mesh to a specific length, but I'm having to tediously move the anchor points on it which is time consuming and inefficient. For example I'm trying to get an even 700 centimeters, but I keep getting around 701.554 or 699.4567 etc.
By displaying edge length in edit mode, you can view the edge length as you move a vertex. In 2.79 edge length can be enabled in the properties region N under Mesh Display, while in 2.80 it is in the viewport overlay menu in the header.
When you are moving a vertex, hold ⇧ Shift to slow down movement so that you can get the exact measurement you are after.
When you are trying to get the sum of multiple edges to equal a certain length, you can create a temporary edge and use snapping to align your vertex to the "measuring" vertex. Constraining movement to a single axis can also make this easier.