No. How many you need to burn to lose weight depends on how much you eat. And how much you need to eat to lose weight depends on how much you burn.
Therefore no system can calculate both for you. :)
Spark chooses to calculate how much you need to eat, given how much you're burning.
Average healthy adults get 30-60 minutes of exercise 5-6 times a week. If you're getting that much, that's fine as far as duration goes. Just make sure you keep challenging your intensity.
Track what you actually DO do for a week, and that'll tell you how much you burn in a week. Put that in as your "calories to burn weekly" goal and update as necessary, and you'll know your calories to eat is as accurate as that can be for your goals.
Remember weight loss is 80% nutrition, not exercise.
Deb, in New Zealand