Range of Delta

For a bull spread , if Long call is in the money and short call is out of money, why the overall delta is then very close to 1

For simplicity, sum up the deltas of both.

You’d have (for example) Delta = 0.98 - 0.05 = 0.93

Thanks a lot MrSmart! To clarify some concept, Long call and short put has + delta , long put and short call has -delta right ?

Right.