The number of calories burned on a rowing machine depends on several factors, such as your weight, the intensity of the workout, and the duration of exercise.

Here’s a rough estimate based on different intensities:

1. Light Intensity: A person weighing around 130 pounds (59 kg) might burn approximately 180-200 calories in 30 minutes.
2. Moderate Intensity: The same person could burn about 220-260 calories in 30 minutes at a moderate pace.
3. Vigorous Intensity: At a vigorous or high intensity, the calorie burn could increase to around 280-320 calories in 30 minutes.

It’s important to note that these are estimated values and actual calorie burn can vary. Factors such as rowing technique, body composition, and the specific settings on the rowing machine (like resistance level) also influence the total calorie burn. For more personalized data, using a fitness tracker or a rowing machine with a calorie counter is recommended.