The Solvent Mole Fraction Calculator determines the mole fraction of a solvent in a solution using the formula X_solvent = n_solvent / (n_solvent + n_solute). Users input the moles of solvent and solute, and the calculator outputs the mole fraction along with the formula substitution. This is useful in chemistry and solution studies for understanding colligative properties, solution composition, and mole-based concentration calculations.