250 milligrammes is equivalent to 0.0525 teaspoons of dry cooking ingredients including sugar, salt, and spice. One gramme, or 1,000 milligrammes, is equivalent to approximately 0.21 teaspoons. A quarter of 1,000 milligrammes is 250 milligrammes, therefore dividing 0.21 by four produces 0.0525.
This is a conversion from mass to volume. Such conversions are not particularly accurate, but for common domestic uses, such as cooking, the variations are typically deemed insignificant enough to be disregarded. Varying ingredients have different mass values per unit volume; hence, a teaspoon of one ingredient may be heavier than a teaspoon of another.
For an appropriate conversion, a cook must have access to a big database of items, preferably at varying temperatures. This is important because many substances expand as the temperature rises, while their mass remains constant, resulting in erroneous conversions.