To know the charging time for your smartphone, kindly follow the below formula.
Formula: power bank capacity X 0.8 (about 20% loss) / mobile phone battery capacity = charging times (approximately)
EXAMPLE: Power Bank capacity 11200mah, Mobile phone battery capacity 3100mAh
Formula: 11200mAh X 0.8 / 3100mAh = around 2.89 times.