im going to work out every day. Cardio and weight training.
For cardio im going to be using a cross trainer. Also i can only work out at night because of work and college.
I weigh 18 stones. 6 ft 1 inch. 18 years old.
i need to know how long i need to exercise please.
Thank you

A pound is 3500 calories. Figure the approximate number of calories you burn per workout. Subtract that from 3500. Divide the remaining number by 7 (number of days in a week). This number is how many calories you need to cut per day to lose one pound of weight a week in combination with your exercise program.
Now, keep in mind that if your are doing weight-bearing exercise, you will be building muscle. Muscle weighs more than fat, but takes up less room on your bones because it is more dense than fat. Muscle also burns calories. The measure on the scale of your total body weight will NOT give you an indication of how much fat you've lost, or of how much muscle you have gained. So overall weight loss is not a good indicator of your progress. Maybe you don't need to lose nearly as many pounds, as you will be developing more muscle mass through exercise.

Working out is only half the equation.
Fat is stored fuel. To get rid of it, you need to take in less than you need for daily activities. You can work out all day long, but if you eat enough, you can still gain weight.
Eat less, exercise more. Any combination will result in weight loss. Its up to you what you personally can manage.

u can lose 2-3 pound by eating healthy and drinking lots of water in a week without working out...so u should set ur goal to 4-5 pounds a week...and for cardio 30 -45 mins

2 hours every other day

Ouch !
Only at night ? I was gonna suggest some cardio in the morning since you can burn more body fat before breakfast. By weight, I'm assuming you mean body fat cause I don't think you would want to loose precious muscles. Work out on cardio for 1-2 hours a days if you want to loose body fat, muscle training also helps but you will gain weight due to the increase in muscle. So I think you should restate your goal to loosing body fat instead of weight unless you dont want your lean body mass.
Good luck :)