How much exercise do you need? The answer is 30 minutes most days of the week, according to government guidelines. But you can calculate your own fitness level by using the aerobic mile as your guideline.

An aerobic mile, simply, is how much energy you expend jogging one mile. Okay, you don’t want to jog. But you can burn the same number of calories by doing other exercises. Here are some examples of activities you can do to equal one aerobic mile:

•  Walking one mile at any pace

•  Bicycling at a moderate pace for 12 minutes

•  Vigorous rowing for 12 minutes

•  Swimming for 24 minutes

•  Tennis for 20 minutes (11 if your game is vigorous)

•  Weight training at a moderate pace for 15 minutes

•  Easy gardening for one hour

•  Aerobic exercise to music, easy pace for 20 minutes

Beginning exercisers should strive to achieve the equivalent of 6 aerobic miles a week. Those with good fitness levels can move up to 10 hours a week. High fitness levels are achieved with 15 aerobic miles each week, according to ACSM Guidelines for Exercise Testing.