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Multiferroic ceramics have been doped with Ca and it is found that the magnetic Neel temperature increases as Ca concentration increases, at a rate of 0.66 K per 1% Ca (molar). The smaller ionic size of Ca compared with Bi results in a contraction of the lattice, suggesting that Ca doping can be regarded as a proxy for hydrostatic pressure, with an equivalence of . Combining these results, we argue that hydrostatic pressure should increase the magnetic transition temperature of at a rate around . Our results also suggest that pressure (chemical or hydrostatic) may be used to bring the ferroelectric critical temperature and the magnetic closer together, thereby enhancing magnetoelectric coupling, provided that electrical conductivity can be kept sufficiently low.