Teaspoon to Milligram Conversion Methodology

A teaspoon measures volume; a milligram measures mass. There is no universal teaspoon-to-milligram conversion without identifying the substance and its density.

Formula

For a US teaspoon, use mg = teaspoons × 4.92892159375 mL × density (g/mL) × 1,000. A metric teaspoon uses 5 mL.

For example, one US teaspoon of an ingredient with density 0.845 g/mL is about 4,165 mg.

Assumptions and limitations

• US teaspoon: 4.92892159375 mL; metric teaspoon: 5 mL.
• Density values are representative and may vary by product, moisture, temperature, particle size, and packing.
• Ingredient pages are measurement estimates, not nutrition labels, prescriptions, or dosage instructions.
• Medicine and supplement pages must not be used to choose a dose. Follow the product label and a clinician or pharmacist.

Reference sources

Unit relationships are checked against NIST measurement guidance and the BIPM SI Brochure. Ingredient density should be verified against the product manufacturer when precision matters.

Continue to the calculator

Use the main teaspoon-to-milligram calculator, or browse the ingredient database.