I’d like to know if anyone has formulas for calculating the spring constant (k) of coil springs, from their physical dimensions. I bought a coil spring, suspended a 0.6 kg mass to it, observed its oscillation period at very close to 0.6 seconds, and so believed the spring constant “k” to be about 65. The spring has a 19mm coil diameter, 22 active coils, the wire is 1mm diameter. Not sure of the shear modulus, but I believe it’s just spring steel. Can’t seem to find a formula that comes out even close to agreement, or even a place that tells the units of measure for their formulas.