Welcome to

Angle of Repose

Definition, measurement, calculation & interpretation

What is the angle of repose of powders or granulates ?

Follow us on Twitter 
Question, remark ? Contact us at

Section summary
1. Powder flowability characterization : angle of repose
2. Calculation formula of the angle of repose
3. Interpretation and relation to flowability of angle of repose

1. Powder flowability characterization : angle of repose

The angle of repose is used an indicator of the flowability of bulk solids such as powders or granulates. It is a quick method that allows to get an idea of the flowability of granular materials.

It's actually important to highlight that there are different angles of repose, depending on the methodology that has been used to measure it. The most common method is to have the material poured freely through a funnel, the material forming a heap. But it is also possible to measure an angle by sliding the material on a plate, using a revolving cylinder, or leaving the powder flow out of a smaller container through a hole.

Angle of repose measurement methods

Figure 1 : Different methods for measuring the angle of repose of powders and granulates

Those different methods are actually giving different values of the angle of repose. It is thus very important to know according to which protocol the angle of repose has been measured in order to be able to compare the flowability of materials. The funnel method (external funnel) is giving the lowest measure of the angle of repose :

External funnel method angle < Internal funnel method angle < Sliding method angle

The lower the angle of repose, the more flowable is a material.

2. Calculation formula of the angle of repose

How to calculate the angle of repose ?

The angle of repose of a material can only be measured through an actual experience. The methodology considered here is the most common, the external funnel method, done by pouring a certain quantity of solid from a funnel and measuring the angle of the heap of material formed.

To be noted that even for this funnel method, there are also some variations in methodology. For example, the funnel can be fixed or can be slowly moved up. A specified height of the heap can be the parameter to stop the experience, or it can be the diameter of the heap formed.

If the angle of repose method is used within a lab to characterize the flowability of different components, it is important to chose one protocol and keep it for all measurement.

The formula to calculate the angle of repose is the following :

Angle_of_repose = arctan(h/r)


h : height of the heap (mm)
r : radius of the heap (mm)

Calculation of angle of repose
Figure 2 : measurement of the angle of repose

3. Interpretation and relation to flowability of angle of repose

The flowability of a bulk solids is estimated by 1st measuring the angle of repose, then referring to the table below to determine in which class is the powder studied :

Flowability expected Angle of repose
Excellent / Very Free Flow 25-30
Good / Free Flow 31-35
Fair (discharging aid may not be required) 36-40
Passable 41-45
Poor Flow / Cohesive (active discharging aid required) 46-55
Very Poor Flow / Very Cohesive 56-65
Approximatively no flow > 66

The table was determined by the authors of the method, by testing different material flowability, and measuring the corresponding angle of repose.

Note that it is an approximate method giving trends, it can happen that a material behave differently once in the process. The characterization of the flowability and the determination of physical parameters allowing the design of hoppers would require a full shear cell testing.

Other methods to define the flowability of powders or granules :


The content of is copyrighted but no warranty nor liability is ensured. The content of this site is to be seen as a help and important information and calculation must always be double checked by the user through the quality procedure of his organization or by checking another source. The user must always respect all applicable regulation. The use of the information is at the user and its organization own risk and own cost.

About privacy and cookies on this site

Our site uses cookies and other technologies from 3rd party companies. Access our Privacy Policy in the "About" page to know more about those cookies and technologies . Further use of this site will be considered consent. is secured by SSL encryption

Follow us on Twitter