Understanding Incline Percentage: What Grade Means
Incline percentage = vertical rise per 100 horizontal units. 100% grade = 45°. Highway grades max at 6-8%, San Francisco's steepest streets hit ~31%.
Incline percentage (grade) measures slope steepness as the ratio of vertical rise to horizontal distance. - 5% grade = 5 units of rise per 100 units of horizontal distance - 10% grade = 10 units per 100 - 100% grade = 45 degrees (rise equals run) The trucking rule of thumb that "each percent is like dragging an extra car" is not literally accurate but gives an intuitive sense of additional effort required. In reality, the additional force needed is proportional to the sine of the angle, which for small grades approximates the grade percentage itself. For context: most highway grades are limited to 6-8%. A 15% grade is considered very steep for roads. San Francisco's steepest streets reach about 31%.