A 65 kg person burns roughly 200-250 kcal an hour on a brisk walk (approximate). So a burger of ~500 kcal is about two hours of walking.
This is meant to give perspective, not to guilt you. Use the Burn it off tool with your own weight.
This is general information, not a substitute for medical advice. If you have a medical condition, are pregnant, or take regular medication, talk to your doctor first.