#### Answer

$500\text{ mg}\approx 0.018 \text{ oz}$

#### Work Step by Step

If want to convert from milligrams to ounces, first we convert from milligrams to grams:
$1\text{ mg}=0.001\text{ g}$
By multiplying both sides by $500$ we get:
$500\text{ mg}=0.5\text{ g}$
After that, we have to consider the following conversion rate:
$28.349\text{ g}\approx 1 \text{ oz}$
By dividing both sides by $28.349$, we get:
$1\text{ g}\approx \frac{1}{28.349} \text{ oz}$
We multiply both sides by 0.5 in order to get the answer to the question:
$500\text{ mg}=0.5\text{ g}\approx \frac{0.5}{28.349} \text{ oz}\approx 0.0176 \text{ oz}$
By rounding it to three decimal places:
$500\text{ mg}\approx 0.018 \text{ oz}$