Embodiments of the present disclosure are directed to polyether-acetal polyol compositions, more particularly to polyol compositions including a polyether-acetal polyol that can be utilized to form polyurethanes. As an example, a polyurethane formulation can include a polyol composition including a polyether-acetal polyol functionalized with at least one acetal functional group, where the polyol composition has an average hydroxyl functionality from 2 to 8 and a hydroxyl equivalent weight from 150 to 4000, where the portion of the polyether-acetal polyol that is functionalized with the at least one acetal functional group is 1 percent to 40 percent of a total weight of the polyether-acetal polyol, where the polyether-acetal polyol has a primary hydroxyl group content of at least 55 percent, and a polyisocyanate, where the polyurethane formulation has an isocyanate index in a range from 70 to 500.