When it comes to burning calories, not all exercises are created equal. Some exercises burn more calories than others, and some can be done in a shorter amount of time. If you're short on time but still want to burn a lot of calories, here are some exercises to try:

1. High-Intensity Interval Training (HIIT): HIIT is a type of cardio that alternates between short bursts of intense exercise and periods of recovery. This type of training can burn a lot of calories in a short amount of time, and it's also been shown to improve cardiovascular fitness.

2. Jumping jacks: Jumping jacks are a simple and effective cardio exercise that can be done almost anywhere. They're great for burning calories and can also help to improve your coordination and balance.

3. Burpees: Burpees are a full-body exercise that work your arms, legs, and core. They're a great way to burn a lot of calories in a short amount of time, and they can also help to improve your cardiovascular fitness.

4. Running: Running is a great calorie-burning exercise that can be done in a short amount of time. Even a short run can burn a lot of calories and improve cardiovascular fitness.

5. Cycling: Cycling is a great low-impact exercise that can burn a lot of calories in a short amount of time. It can be done indoors or outdoors and is a great way to improve cardiovascular fitness.