There are a lot of factors that can influence your ideal snowboard length. Getting on the right size snowboard is an important part of being comfortable and enjoying your time on the slopes. Using your height is a good starting point and taking things into consideration like weight, ability level, terrain, and even your personal style of riding will help to narrow down your size range. For most people their starting point will land somewhere between their chin and nose. Remember, these are just guidelines, not rules. If you have a preferred size that you are comfortable on you can certainly go with that.
Beginner: If you are a beginner looking for a board that is easy to maneuver and keep in control, consider sizing down 5-10cm from your starting point. This will usually put the board at chin height or a little below. This is a common practice at resorts and rental shops as it helps to build the confidence and essential skills a rider needs to move beyond the bunny slopes.
Intermediate: Are you an intermediate rider who has mastered the basics but is still progressing? Choosing a size that lands between chin and nose height will give you the length needed for stability on faster intermediate terrain but keep the board from being too unforgiving when mistakes are made.
Advanced: If you are an advanced rider you probably have a good idea of what you need in a board. A longer length is usually preferred as conditions become more demanding and the additional stiffness and stability of a longer board is necessary. This will typically mean a board length that is about nose to eye height.
Conservative: If you prefer to stick to the groomers a shorter board may be for you. Keeping your turns short and going at a moderate speed means that a board at or slightly below chin height would more suited to your style.
Aggressive: Sometimes there are those that just wanna go fast. If you are spending most of your time riding at high speeds on steep or technical terrain and carving aggressively, selecting a size that is nose to eye height or slightly above will give the added stiffness and stability that is needed for this style.
Groomed: For riders that spend a majority of their day on groomed, hard packed, or icy surfaces, going with a standard length is best. A standard length will keep the board maneuverable and help maintain a good edge hold.
Powder: When you spend a lot of time in fresh snow or off trail a slightly longer board will give you that extra bit of float to keep you moving through the deep stuff. You will also want to consider a board with a wider waist width or powder specific shape that will also help you float and keep you on the surface.
If you are above or below the average weight for your height you should adjust your size accordingly. If you are above the average weight for your height you can consider a longer board for added stability and response. If you are below the average weight for your height you can go with a shorter board to get the flex and maneuverability you need.