Hi.
Just count how many drops that 1 mL contains.
With the dropper I got from Kirkland minoxidil I counted the following.
1 mL (50 mg) = 24 drops
Therefore, each drop contains approximately 2 mg of minoxidil.
Now something that might help you.
Currently I'm taking 3 drops (6 mg) orally every morning and also apply 1 mL topically. If I do this at night, the next morning I wake up with puffy eyes, but If I do it in the morning, I get no puffy eyes.
Possible explanation is that when we're laying down, the blood flow to our head/scalp is already more than enough, we only need to increase it when we are standing up. Gravity...
Another tip.
Minoxidil will increase your heart rate, it's like you're overclocking your heart. That's another reason why I take it when I'm starting the day, not at the end.
Moreover, If I take minoxidil orally and don't exercise in that day I'll get headaches (probably too much blood flow in the head)... a good 30 minutes walk is enough to have your leg muscles using that extra blood flow and avoid headaches, but I try to walk at least 1 hour every day.
You definitely don't want a fast heart rate when you're trying to sleep. Always use minoxidil in the morning!