You can't really for a number of different reasons. Firstly, teaspoons are not real accurate measurements. Not only do they differ in size slightly due to the style in which they have been made, but also the measurement varies dependant on how the teaspoon is filled (heaped, level etc). Secondly these two measurements do not conform (a teaspoon is a volumetric measure, milligram is mass). Thirdly, milligrams are tiny measurements and so to actually fill one teaspoon would be quite a lot of milligrams (therefore you would probably be better to convert grams to teaspoons instead).
If you still wish to attempt to convert milligrams to teaspoons (although the measurement is not likely to be accurate) it is probably easiest to measure one teaspoon of sugar for instance and then weigh using your kitchen scales. The measurement will likely be in grams; if so you will then need to divide this by 1000.
If this is a question related to medicines, you will need to convert into millilitres as opposed to milligrams. Converting liquids into teaspoon measurements is much easier; an average teaspoon roughly equates to 5ml of a given liquid. This conversion is often needed when taking medication, as the label will often give dosage in ml; despite the fact many people do not have a means of measuring such quantities accurately. This conversion is therefore useful in calculating how much medication to take.
If you still wish to attempt to convert milligrams to teaspoons (although the measurement is not likely to be accurate) it is probably easiest to measure one teaspoon of sugar for instance and then weigh using your kitchen scales. The measurement will likely be in grams; if so you will then need to divide this by 1000.
If this is a question related to medicines, you will need to convert into millilitres as opposed to milligrams. Converting liquids into teaspoon measurements is much easier; an average teaspoon roughly equates to 5ml of a given liquid. This conversion is often needed when taking medication, as the label will often give dosage in ml; despite the fact many people do not have a means of measuring such quantities accurately. This conversion is therefore useful in calculating how much medication to take.
