The prefix "micro" in the SI system denotes a factor of 10-6, which is written as 1E-6 in exponential notation.

Therefore, one microgram is equal to 10-6 grams of force.

The prefix "milli" in SI notation denotes a factor of 10-3, which is written as 1E-3 in exponential notation.

Therefore, 1 milligram is equal to 10-3 grams of force.

To convert from micrograms to milligrams, you divide the number of micrograms by 1000. One milligram is equal to 1000 micrograms. Here is the formula for converting micrograms to milligrams, sometimes known as the mcg to mg formula:

micrograms ÷ 1000 = milligrams

mcg ÷ 1000 = mg

To convert 400 micrograms to milligrams, we enter 400 into our formula to get the answer as follows:

mcg ÷ 1000 = mg

400 ÷ 1000 = 0.4

400 mcg = 0.4 mg

Now you know that 400 micrograms equal 0.4 milligrams.

Using online calculators like https://mycalcu.com/ you can convert any amount of micrograms to milligrams.