  We analyse fluctuations about $T_c$ in the specific heat of
(Y,Ca)Ba$_2$Cu$_3$O$_{7-\delta}$, YBa$_2$Cu$_4$O$_8$ and
Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. The mean-field transition temperature,
$T_c^{mf}$, in the absence of fluctuations lies well above $T_c$ especially at
low doping where it reaches as high as 150K. We show that phase and amplitude
fluctuations set in simultaneously and $T_c^{mf}$ scales with the gap,
$\Delta_0$, such that $2\Delta_0/k_BT_c^{mf}$ is comparable to the BCS
weak-coupling value, 4.3, for d-wave superconductivity. We also show that
$T_c^{mf}$ is unrelated to the pseudogap temperature, $T^*$.
