Universal formulas for percolation thresholds

A power law is postulated for both site and bond percolation thresholds. The formula is p(c) = po[(d - 1)(q - 1)](-a)d(b), where d is the space dimension and q the coordination number. All thresholds up to d --> infinity are found to belong to only three universality classes. For two classes b = 0 for site dilution while b = a for bond dilution. The remaining class associated with high dimensions is characterized by b = 2a - 1 for both sites and bonds. Classes are defined by a set of value for {p(0); a}. Deviations from available numerical estimates at d less than or equal to 7 are within +/- 0.008 and +/- 0.0004 for high dimensional hypercubic expansions at d greater than or equal to 8. The formula is found to be also valid for Ising critical temperatures.