I use the formula below, which was originally posted by Joanne. This seems far more accurate than a machine estimating calories burned.

Activity points for light intensity = [your weight] x [minutes] x 0.00023
Activity points for moderate intensity = [your weight] x [minutes] x 0.00033
Activity points for high intensity = [your weight] x [minutes] x 0.00081

Since you wear a monitor anyway, and since sometimes it’s hard to know how hard you’re working, here’s something else that might be useful to you. To factor whether I’m working out at high, moderate, or low intensity, I use the following formula to calculate my own personal heart rate targets (credit goes to Joanne for this one, too):

For moderate-intensity physical activity, a person’s target heart rate should be 50 to 70% of his or her maximum heart rate. This maximum rate is based on the person’s age. An estimate of a person’s maximum age-related heart rate can be obtained by subtracting the person’s age from 220. For example, for a 50-year-old person, the estimated maximum age-related heart rate would be calculated as 220 — 50 years = 170 beats per minute (bpm). The 50% and 70% levels would be:
50% level: 170 x 0.50 = 85 bpm, and
70% level: 170 x 0.70 = 119 bpm

Thus, moderate-intensity physical activity for a 50-year-old person will require that the heart rate remains between 85 and 119 bpm during physical activity.

For vigorous-intensity physical activity, a person’s target heart rate should be 70 to 85% of his or her maximum heart rate. To calculate this range, follow the same formula as used above, except change «50 and 70%» to «70 and 85%». For example, for a 35-year-old person, the estimated maximum age-related heart rate would be calculated as 220 — 35 years = 185 beats per minute (bpm). The 70% and 85% levels would be:
70% level: 185 x 0.70 = 130 bpm, and
85% level: 185 x 0.85 = 157 bpm

Thus, vigorous-intensity physical activity for a 35-year-old person will require that the heart rate remains between 130 and 157 bpm during physical activity.

Have fun!

Sue