There is no definitive answer to this question as the size of a riser platform depends on a number of factors, including the height of the stage, the width of the stage and the number of risers required. However, there are some general guidelines that can be followed when deciding on the size of a riser platform.
The first step is to determine the dimensions of the stage. The stage should be big enough to accommodate all of the performers and equipment that will be used during the performance. Once you have determined the size of the stage, you can then start to plan for the size of your riser platform.
A good rule of thumb is that each riser should be able to accommodate two people comfortably. This means that if you have a stage that is 10 feet wide, you would need a riser platform that is at least 5 feet wide. If you have a taller stage, you may need wider risers or more risers in order to make sure everyone has enough space.
Another factor to consider when choosing your riser platform size is how many people will be using it at once. If you only have a few performers, you may not need as large of a riser platform as if you had dozens or even hundreds of performers. Keep in mind though that larger platforms can always be divided into smaller sections if needed.
In general, most standard riser platforms are between 4 and 8 feet wide and between 2 and 4 feet tall. However, these dimensions can vary depending on your specific needs so it's important to work with a professional designer or architect to make sure your platform meets all code requirements and provides enough space for your performers.