1 part portland cement to 1 part fine graded sand is used for grout joints up to 1/8 inch (3 mm) wide.  1:2 for joints up to 1/2 inch (12.5 mm) wide, and 1:3 for grout joints over 1/2 inch (12.5 mm) wide.  Up to 1/5 part lime may be added.

Standard factory mixed grouts normally have polymers and other water retentive chemicals to the grout that makes it harder, more stain resistant, and more consistent in color if cured properly.