Yes you need to burn 3500 calories to lose a pound of fat or be in a 500 calorie deficit but the key is to figure out as a baseline how many calories you are burning on a daily basis. If you know how many calories you burn then you can easily adjust calories consumed to be 500 calories below what you burn to lose 1 lb of fat per week. Of course the more calories your body burns the more food you can take in. All calories burned calculators are estimates and should not be taken hook, line and sinker.
The best method to figuring out calories burned is by testing. If you average 2000 calories consumed per day but do not lose a lb of fat then chances are you are not burning 2500 calories per day. However if you consume 2000 calories per day and burn more than a lb of fat per week then that means you burn more than 2500 calories per day. It takes some testing but once you figure out how many calories approximately you burn per day you can accurately gauge your intake.
Below are two links:
- Is a calculator for figuring out basic metabolic rate and resting metabolic rate
- Is a link to the Exerspy by dotFIT which is a device which accurately gauges the amount of calories burned in a daily basis.