Metal Foam Calculator: Porosity, Density & Surface Area
Convert nickel, copper or iron foam specifications in one step: porosity and density from areal density and thickness, cell size from PPI, an estimate of geometric surface area, and what happens to porosity when you calender the foam for an electrode.
Your foam
Values above are example inputs, not a product specification. Enter the figures from your datasheet or measurement.
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Formulas
The surface-area constant comes from a tetrakaidecahedral (Kelvin) cell of edge length l with 12 struts per cell: φ = 3πr²/(2√2·l²), S_v = 3πr/(√2·l²), and an equivalent-sphere cell diameter d = 2.785·l.
Questions
How do you calculate the porosity of nickel foam?
Porosity = 1 − (areal density ÷ (thickness × solid density)). With areal density in g/m², thickness in mm and solid density in g/cm³: apparent density (g/cm³) = areal density ÷ (thickness × 1000). Example: 350 g/m² nickel foam at 1.6 mm has an apparent density of 0.219 g/cm³; divided by nickel's 8.908 g/cm³ that is a relative density of 2.5%, so porosity is about 97.5%.
What does PPI mean for metal foam?
PPI is pores per linear inch. The nominal cell size is roughly 25.4 mm ÷ PPI, so 110 PPI is about 0.23 mm and 20 PPI is about 1.3 mm. Suppliers measure PPI in different ways, so treat it as nominal.
How is the specific surface area of metal foam estimated?
This calculator uses a Kelvin-cell (tetrakaidecahedron) model with solid cylindrical struts: geometric surface per volume ≈ 10.17 × √(relative density) ÷ cell diameter. It gives the outer geometric surface of the struts, not BET surface area. Real foams with triangular or hollow struts have somewhat more outer surface, so treat the result as an estimate and measure when it matters.
What happens to porosity when nickel foam is compressed or calendered?
Mass per area stays the same, so porosity after rolling = 1 − (areal density ÷ (new thickness × 1000 × solid density)). Halving the thickness doubles the apparent density. Cells flatten, so the PPI value no longer describes the compressed foam well.
Which solid densities are used?
Nickel 8.908 g/cm³, copper 8.96, iron 7.874, 304 stainless steel about 7.93 and aluminium 2.70. For alloys such as nickel-iron, enter your alloy's density.
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