To weight small quantities of substances, you need in general a precision scale, witch is not a common domestic object. But a scale to weight with precision more than, let us say, 10 or 20g a common kitchen scale is enough.
If you then need to weight just 0,5g of a substance you may dissolve 10g in 100 ml of water and use just 5 ml of this solution. If you need 4,5 g, you can dissolve also 10g in 100 ml and use 45ml and so on.
Adopting the rule of 10g/100ml solution you only multiply the amount in g by 10 and you have the amount in ml.
If, instead 10 your scale is weighting 11 because it is not precise, instead of the 0,5 you will be putting 0,55, only 10% more, waht is not so bad. But if you try to weight 0,5 and you fail 1 g it is then a very large mistake, 3 times more.