Calculate drainage pipe fall, gradient ratio, slope percentage, drop per metre or foot, angle, and true pipe length in metric or imperial units.

Required: horizontal run and gradient ratio.
Use the level horizontal distance, not the sloped pipe length.
Enter 60 for a 1:60 fall.

Related Calculators

Drainage Fall Formula

The following formula is used to calculate the drainage fall:

F = (G / 100) * D

Variables:

  • F is the fall (meters)
  • G is the gradient (%)
  • D is the distance (meters)

To calculate the drainage fall, multiply the gradient percentage by the distance and then divide by 100 to convert the percentage to a decimal.

What is Drainage Fall?

Drainage fall is the measure of vertical drop within a drainage system over a certain distance. It is an important aspect of civil engineering and building design, ensuring that water flows away from structures effectively. The gradient is typically expressed as a percentage, representing the ratio of the fall to the horizontal distance.

How to Calculate Drainage Fall?

The following steps outline how to calculate the Drainage Fall.

  1. First, determine the distance (D) over which you want to calculate the fall, in meters.
  2. Next, determine the gradient (G) of the drainage system as a percentage.
  3. Use the formula F = (G / 100) * D to calculate the fall (F).
  4. Finally, calculate the Drainage Fall (F) in meters.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Distance (D) = 50 meters

Gradient (G) = 2%

Using the formula, the fall (F) would be calculated as follows:

F = (2 / 100) * 50 = 1 meter