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/ft3, 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/ft3, meaning 4 pounds per cubic foot
  • 64 kg, or 64 kg/m3, 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/ft3 foam can also be said to be 64 kg/m3.

 

Unit

LB

Kg

Specific density

Expansion ratio

Description

lb/ft3

Pounds per cubic foot

Kg/m3

Kilograms per cubic meter

g/cc

Grams per cubic
centimeter

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