The way to tell what the moisture level is to measure the water content with a refractometer.
There are many refractometers used in many different industries. Refractometers are used in the food, HVAC, and the machine tool industries to name a few. Refractometers can be specific to what is needed to be tested.
In the honey world, we need a refractomer that is specific to honey. Other refractometers look the same but they would not work to measure water in honey. So if you see one for sale on EBay you better know what you are buying. Every year I have beekeepers bring me their refractometers because they can't read it. Only to find out that they purchased the wrong one.
Refractometers do have to be calibrated with a glycerin calibrating solution. Not calibrating the instrument can lead to a bad reading and your honey may not be U.S. Grade A. A tiny vial of calibrating solution costs about $10.00.
I have a high end refractometer, like the one below. I calibrate it every year at the start of the honey season. It is very accurate and holds its calibration very well. I usually never have to change the adjustment. When you get to cheaper refractometers, the need to calibrate them before each season is imperative.
At Nature's Nectar LLC we do moisture check honey samples for free. If you can't drive here, you can mail me a sample and I will call, text or email the results back to you. I need a thimble size of honey for a sample. The sample should pretty much fill the container. Don't bring a thimble size container in a quart canning jar for example. Any humidity in the jar will absorb into the honey, making the test inaccurate.
Refractometers sell for $75.00 up to over $400.00. The one below costs over $400.00. We do sell the $75.00 refractometer in our store and I will calibrate it for free if you buy it from us. No other bee store offers this service.