Write down the substance’s volume amount in teaspoon measurements.
Example: 3 tsp.
Divide the teaspoon amount by 4.929. The result is the equivalent volume amount in milliliter measurements. Milliliters belong to the metric system unit of measurement.
Example: 3 / 4.929 = 0.609 ml
Write down the substance’s density measurement in grams per millimeter units (g/ml).
Example: 0.5 g/ml
Multiply the volume measurement in milliliters by the substance’s density. (The formula for mass is volume * density = mass.) The result is the substances mass measurement in grams.
Example: 0.609 * 0.5 = 0.3045 g
Multiply the mass measurement in grams by 1000. The result is the mass measurement in milligrams.
Example: 0.3045 * 1000 = 304.5 mg