There are many considerations in deciding what fabric to choose for your hammock.
You will need to weigh options like weight, durability, and strength of the fabric, and also consider your own weight and height to ensure that your chosen fabric is supportive enough and wide enough for your needs.
We don't use a weight rating to help you determine what fabric you should get, instead, we have developed a comfort rating. All fabrics have a different levels of support, durability, stretch, and strength, all of which will effect how comfortable you are in a hammock.
While even though our lightest fabrics would probably hold most people off the ground, many would experience a lot of stretch from fabrics that are too light for them. The comfort rating helps you determine whether the fabric is supportive enough for you. A fabric that isn't supportive enough will stretch, causing you to feel like your laying in a bowl with your shoulders squeezed together, and your spine curved, and it will be much harder to move around and shift positions.
The calculator will show you the maximum weight, but it never hurts to go with a more supportive fabric. For example, I am about 160 lbs, and I prefer 1.7 Mtn-XL (325 comfort rating) over HyperD (260 comfort rating). While I get by just fine with 1.6 HyperD, I really like the extra support I get from 1.7 Mtn-XL with only a little bit of extra weight.
I recommend prioritizing comfort over weight. I always tell people that shaving off a few ounces off their pack weight will help you walk 1 extra mile each day, but having a good nights sleep will help you hike 3 extra miles!