The number of teaspoons in 1 pound of a substance is the reciprocal of the substance's density in pounds per teaspoon. Because teaspoons are a measurement of volume and pounds are a measurement of mass, the number of teaspoons in a pound depends on the density of the substance in question.
Pounds per teaspoon is not a standard form of measurement for density, so conversion must take place before the number of teaspoons in 1 pound can be calculated. A more frequently used unit for density is pounds per cubic foot; there are 5,745.04 teaspoons in a cubic foot, so calculating the teaspoons in 1 pound of a substance means dividing 5,745.04 by the density in pounds per cubic feet. This indicates that there are 127.67 teaspoons in 1 pound of brown sugar, 176.77 teaspoons in 1 pound of wheat flour or 287.25 teaspoons in 1 pound of ground coffee.