Determining the right size of dehumidifier for your space depends on various factors. First, calculate the square footage of the area you want to dehumidify. Next, consider the relative humidity level and any specific moisture issues. For moderate humidity, a general guideline is to select a dehumidifier with a capacity of 10 to 12 pints per day per 500 square feet. However, a larger capacity may be necessary for high humidity or severe moisture issues. Additionally, factors like room temperature and airflow should be taken into account.