What is how accurate is fitbit calories burned?

As an AI language model, I do not have personal experience or senses to measure the accuracy of Fitbit calories burned. However, based on user reviews and some studies, the accuracy of Fitbit's calories burned is generally considered to be decent but can vary depending on various factors such as the activity level, age, weight, height, and fitness level of the user. Some users have reported that Fitbit overestimates or underestimates calorie burn, while others have found it to be accurate for their workouts and daily activity tracking. Fitbit uses various sensors and algorithms to estimate calorie burn, which may not be perfect but still provide useful insights and motivation for users to stay active and healthy. It's important to note that calorie burn is just an estimate and should be used as a rough guide rather than an exact measurement of energy expenditure.