IFD (Indentation Force Deflection), also known as ILD (Indentation Load Deflection), is used by flexible foam manufacturers to gauge the “softness” of their products. The amount of pressure needed to indent a four-inch piece of memory foam by 25% is used to calculate IFD. To carry out this test, pressure is exerted over a 50-square-inch region, and the resulting pressure is then converted into weight. This weight is recorded as the IFD seen on mattresses sold by foam manufacturers.
What can Influence IFD Grading?
Because of the factors that affect a foam’s conditioning, or the setting in which it was kept prior to testing, the IFD grade is typically given as a range, such as 10–12.
The following are variables that can affect IFD grading.
- Thermodynamics and humidity
- How the foam was made
- The material’s thickness
- The company that makes it
How is IFD Grade Obtained?
For measuring IFD, an indentation penetrometer is used to compress a foam with a surface area of 15 × 15 and a thickness of 4 inches. The foam is put on the penetrometer’s perforated base before testing, which allows air to escape during the compression process. After being warmed, the foam is compressed to 25% of its original thickness. It is recorded how much force was required to compress this foam. The foam is further compressed to 25–75% of its original thickness. The foam is compressed to 65% of its initial thickness in the final stage, and after one minute, the result is recorded as the IFD grade.
What do IFD Gradings Mean?
IFD is a consistent method for measuring mattress foam thickness, applicable across different manufacturers.
IFD scores are correlated to the firmness of mattresses as follows.
- Extra plush- <16.5 (lbs)
- Plush- 16.5-22.5 (lbs)
- Soft- 22.5-26.5 (lbs)
- Medium- 25.6-30.5 (lbs)
- Firm- 30.5-34.5 (lbs)
- Extra firm- 34.5-38.5 (lbs)
