In general, for a slide that extends straight out, you can determine the Slide Reach (the distance the slide sticks out from the deck) by multiplying the slide length by 0.866. For example, if your slide is 10 ft long, the Slide Reach will be approximately 8'-8".
Some exceptions to this rule include spiral slides, which have a different type of footprint, and slides that mount to shorter and taller deck heights which may reduce the steepness of the slide angle for safety reasons. In most cases, we strive to include this information on the product page so you can know the specific measurements for each slide.