Impossible to say, really. You can calculate the LD50 using your body weight (LD50's are given by mg/kg so however many milligrams it is, you times that by your weight in Kg (or your weight in lbs X'd by 2.2)).
But it doesn't take into consideration your tolerance and that's not really something that can be accurately, scientifically measured. Plus everyone naturally reacts differently to different drugs and have different sensitivity levels.
Also, the LD50 is only the dose than would kill 50% of people who took it, so it's no guarantee.
The best bet would be to IV a macro-dose (basically "hot shot" yourself) like if you inject like a couple grams of morphine or a few hundred mg of Fentanyl, nobody could survive that.
80mg of IV Morphine has been reported as the minimum dose to kill an average sized adult with zero tolerance.
Of course the chances of a fatal OD would increase exponentially if you also took Barbiturates. Just three times the highest prescription daily dose of a barbiturate alone can kill.
The chances would also drastically increase if any of CNS depressant were used such as alcohol, benzo's, GHB, Gabapentinoids etc.
Although, the actually advise the use of milk, no alcohol (or GHB) as alcohol makes it very likely that one would vomit up any pills taken. Preferably also with a potent anti-emetic.
AGAIN, JUST TO REITERATE WHAT OP STATED, THIS IS ENTIRELY HYPOTHETICAL AND NOT ADVICE.