Density cross reference
Let’s talk about density. What does a 0.064 specific density callout mean?
Density is the most common definition of a foam grade; it means the weight of the foam per a given volume. For example, “4 lb” foam has a weight of 4 pounds per cubic foot, abbreviated to 4 lb/ft^{3}, and then simply to “4 lb”. In North America, the “lb” designation is by far the most commonly used. However, there are four different ways that the same density foam might be called out on a drawing. In rough order of occurrence of the terms on North American drawings:
 4 lb, or 4lb/ft^{3}, meaning 4 pounds per cubic foot
 64 kg, or 64 kg/m^{3}, meaning it weighs 64 kilograms per cubic meter
 0.064 specific density, or 0.064g/cc, meaning it weighs 0.064 grams per cubic centimeter. Water weighs exactly 1g/cc, so this foam weighs 0.064 times the weight of water
 15x expansion ratio, meaning the plastic has been expanded to 15 times of it’s original volume
All densities of foam can be expressed in all four units of measure. Just like a 2 liter bottle of a soft drink also can be said to have 67.6 fluid ounces, the same 4 lb/ft^{3} foam can also be said to be 64 kg/m^{3}.
Unit 
LB 
Kg 
Specific density 
Expansion ratio 
Description 
lb/ft^{3} Pounds per cubic foot 
Kg/m^{3} Kilograms per cubic meter 
g/cc
Grams per cubic 
Factor of Volume expansion during foaming 
Factor 
1 
16.02 
0.016 
58.4 
Density 
1.3 
21 
0.021 
45 
1.5 
24 
0.024 
39 

1.7 
27 
0.027 
34 

1.9 
30 
0.030 
31 

2 
32 
0.032 
29 

2.2 
35 
0.035 
27 

2.3 
37 
0.037 
25 

2.8 
45 
0.045 
21 

3 
48 
0.048 
19 

3.8 
61 
0.061 
15 

4 
64 
0.064 
15 

5 
80 
0.080 
12 

6 
96 
0.096 
10 

8 
128 
0.128 
7 

9 
144 
0.144 
6 

15 
240 
0.240 
4 