You mention no device, and since there are different models, it depends.

Step-based calorie burn for those devices would obviously be grossly underestimated since very few steps for workout, and it's not step based anyway.

HR-based will be inflated, as those formula's only are good estimates for the steady-state aerobic exercise they were developed from.
Lifting (and intervals) is opposite of steady-state HR the same for 2-4 min, and it's anaerobic.

For both of those - you can start your Activity Record so you have start and duration times.
And then manually log a workout with the same for Weights (if reps 5-15 and sets and rests 2-4 min), or Circuit training (if reps 15 over and rests 1 min or less), or calisthenics (if reps over 20 and less than 1 min).

Forgot the one recent model that appears to use that database formula for the time when you start the activity record as weight lifting - it logs the HR of course, but doesn't use HR-based calorie burn.

After you log the workout, you can leave the Activity Record for HR info if desired - your workout replaced the calories in the record.