How Many Calories Does Exercise Actually Burn?

Exercise burns calories, but almost certainly less than you think. Cardio machines, fitness trackers and apps routinely overestimate burn, sometimes by large margins. Understanding the real numbers keeps you from accidentally eating back your entire workout.

The overestimation problem

Studies have found some wrist-worn trackers overestimate calorie burn by 20–90%. Cardio machines are often generous too. The number is a rough guess based on averages, not a precise measurement of your body.

Realistic ballparks

Actual burn depends on your size, intensity and fitness, but for a rough sense: a 30-minute brisk walk might burn 120–200 calories, a hard 30-minute run 300–400, and a weights session less than people expect. These are smaller than a single indulgent snack.

Why “eating back” calories backfires

If your tracker says you burned 500 calories and you eat an extra 500 to “refuel,” you can erase your entire deficit — especially since the 500 was likely overstated. This is one of the most common reasons exercise doesn’t lead to weight loss.

The better approach

• Set your calorie target based on your overall activity level, and don’t add food for each workout.
• Treat exercise as a bonus for health and muscle, not a license to eat more.
• If you do eat back calories, count only a fraction (say half) to stay safe.

Because the burn side is so unreliable, the intake side is where control lives. Logging what you eat with Fotocal is far more accurate than trusting a calorie-burn estimate.