Virtually all query letters should fit into one page of 12-point type single-spaced Times New Roman, including a paragraph for your author bio. And, unless an agent specifically asks for either more or less, your synopsis should fit into 3-5 pages of 12-point type double-spaced. However, both these essential tools in the writer’s toolbox also have their own specific design requirements.
I estimate 4 hours to write your query letter and synopsis.