To convert resistance data into resistivity, you need to know the dimensions of the material and its geometry. Resistivity is the inherent property of a material that describes how much resistance it offers to the flow of electric current. It is given by the following equation:

ρ = RA/L

Where ρ is the resistivity, R is the resistance of the material, A is its cross-sectional area and L is its length (the length between two voltage probes).

For example (see the attached figure), suppose you have a rod-shaped sample with a height (h) = 1 mm and a weight (w) = 0.5 mm and a length (L) = 3 mm. Then the cross-sectional area is A = w .h ( mm²) = (0.001 . 0.0005) m, and you measure the resistance R = 500 Ω. To convert this resistance data into resistivity, use the following formula:

ρ= RA/L = (1000 Ω)(0.0000005 mm²)/(0.003 m) = 0.083 Ωm.

The specific resistance of the wire is therefore 0.083 Ωm.