Pellet Durability Index (PDI) Calculator

What PDI measures

Pellet Durability Index tells you how well a pellet holds together from the mill to the animal. Every transfer, drop, and auger turns some pellets back into fines, and fines are wasted energy, dust, and lost feed value. PDI puts a number on that. It is the percentage of a pellet sample that is still whole after a standard agitation test.

How the test works

The idea is simple. Take a sample, remove the fines it already has, put it through a controlled amount of handling, then measure how much is still whole:

1. Sift the sample to remove the fines it already has.
2. Weigh the clean, sifted sample. This is your before weight.
3. Tumble or agitate it a set amount.
4. Sift again and weigh only the whole pellets. This is your after weight.

PDI is then the after weight divided by the before weight, as a percentage. The two common methods are the tumbling box (ASABE, 500 g tumbled about 10 minutes) and the Holmen tester, which blows pellets around a chamber for a set time. The Holmen is faster and usually reads a few points lower, so always compare results from the same method.

What is a good PDI?

Targets depend on the product and how far it has to travel. Use these as a general guide, not a hard spec:

Product	Typical target
Aquafeed and export pellets	98%+
Poultry and swine feed	95 to 98%
General farm feed, short haul	90 to 95%
Below 90%	Review the process

How to raise a low PDI

If your durability is low, the usual levers are conditioning, die, and formula. Wetter, hotter conditioning builds a stronger pellet, so start there. A higher die compression ratio makes a harder pellet, and the right binder in the formula holds it together. Grind and roll setting matter too. It is the same set of controls that drive the rest of pellet quality.

Note: PDI is only comparable within the same test method and settings. Use it to track your own process over time and to compare against your customer's spec, not as an absolute grade.