To find out how many milliliters are in 1 gallon, we can use the conversion factors provided:
1 gallon = 4 quarts
Since we know that:
1 quart = 946.35 milliliters
We can calculate the milliliters in one gallon:
\[ 1 \text{ gallon} = 4 \text{ quarts} \times 946.35 \text{ mL/quart} \]
Calculating this:
\[ 4 \times 946.35 = 3785.4 \text{ mL} \]
Therefore, the answer is 3785.4 mL.