First, let's find out how heavy just one banknote is. I had a new uncirculated 50 peso bill in my bag so I folded it and weighed it on an analytical balance at school.



So now we know the weight of a banknote will depend on its denomination and whether it is new or worn out. But for the sake of convenience, since a new banknote weighs just under 1 g and an old one just over 1 g, it is very safe to assume that a piece of banknote weighs 1 gram.
Now, how heavy is 1 billion pesos?
If 1 banknote weighs 1 gram, a standard bundle of 100 one thousand peso bills (100,000 PHP) will weigh 100 grams. A million will then be 1 kilogram - easily fits in your bag! But a billion? That will be 1,000 kilograms or one metric ton of 1000-peso bills! That's equivalent to the weight of 20 sacks of rice! You will need a forklift for that.
Lastly, consider that the Bangko Sentral ng Pilipinas (BSP) admits there is currently a shortage of 1000-peso bills, so your 1 billion pesos in cash will most likely be composed of 500-peso bills and weigh 2 metric tons.
Next time, we will imagine together how this 1 billion pesos in cash would look like. Or maybe a trillion?