You could Google is, I think it is called your BMR, Base Metabolism Rate. Just do a quick google and you'll find some sites.
Although none will predict it 100%, probably at best like 80%. You'll have to test it more then likley.
Some of them will have Activitys you can list and it will give a closer number to your BMR. I think you'll type in age and weight, and then one I went too, didn't book mark it, let you type in your typical workload for a day. But if you have a fast metabolism or a slow one it'll be hard to pinpoint. You'll have to spend some time just messing with the numbers and seeing what you can do.