If you're making an everyday recipe from a European cookbook, you can memorize a simple rule to convert milliliters (mL) to teaspoons: five milliliters equal one teaspoon. However, if you need precise measurements for baking or cooking for a large crowd, or for a scientific experiment, you may have to do a little math. Otherwise, the tiny difference in volume between five milliliters and one teaspoon could add up to a big mistake.
Check your recipe or instructions to see how many milliliters you need to convert.
Divide the number of mL you need to convert by 4.92892183. This conversion factor is the actual metric volume of a teaspoon. If you need to convert 10 mL to teaspoons, divide 10 by the conversion factor to see that 10 mL equals precisely 2.02884128 teaspoons.
Convert teaspoons back to mL by multiplying the number of teaspoons by the same conversion factor (4.92892183). For example, to convert two teaspoons into mL, multiply two times the conversion factor to see that two teaspoons equals precisely 9.8578436 mL.