Presented are simple explicit relations for the equilibrium fugacity of single-component (single-guest) gas hydrates as a function of temperature. It is shown how relations of the form ln f = alpha + beta/T can be derived starting with a standard statistical-thermodynamic model based on the van der Waals-Platteeuw equation. In addition to this demonstration of the validity of empirical relations that have been previously presented in the literature for bulk hydrates, explicit relations of the form In f = alpha + beta/T + delta/rT (where r is the pore radius) are derived for hydrate formation in porous media. The validity of these explicit relations is established for both structure I and structure II hydrates involving hydrocarbons that have negligible water solubilities by comparison of predictions for bulk hydrates with experimental data. In addition to their ease of use, these relations explicitly show the role played by the standard model parameters in the prediction of hydrate equilibrium conditions.