You can actually google the estimated living cost in Singapore. However, the cost actually varies as it depends on where and how you're going to spend your money.
For instance, if you were stay in a hostel + regular 3 days meal and nothing else, you might only need about $1000.
However, if you're going to have personal use, transport, hostel fee, meals fee and others, excluding school fees, you might actually need up to $2500.
It also depends on how you're going to spend your money and if you're studying in private schools or government schools.
I'm a Singaporean and I'm studying at a private school which my tuition fees is actually around $6500+- and not to mention I need about $150++ for my transportation. As I need to top up $20 every 4 days. But if you live near your school, then your cost for transportation is definitely lower. My monthly allowance is only $240 including paying for my own phone bills which makes me left with $190. For a whole month, I need to use $190 and it is really never enough for me. I mean like, you need to hang out with friends and buy your own personal use such as clothes as well as for your own meals. And if one of your friends birthday is coming, that's another area where you need to use your money. So the expenses to live in Singapore or rather, any countries varies depending on how you are going to use your money.