For the record, yes, walking is a legit way to be physically active. Like many cardiovascular exercises or activities, walking at an appropriate intensity can help to strengthen your heart and make it more efficient, burn some extra calories, improve respiratory functions, and even elevate your mood through the release of endorphins, says Doug Sklar, a NASM-certified personal trainer and founder of New York City fitness training studio PhilanthroFIT .

Of course, theres a huge difference between going for a leisurely stroll and walking like you mean it. Heres what you need to know about walking for exercise, plus how to max out your walking workout.

You can actually burn more calories walking than youd think.

Things like your weight, metabolism, speed, and the incline youre walking on matter when it comes to calorie burn, says Albert Matheny , RD, CSCS, nutritional advisor to Promix Nutrition and co-founder of SoHo Strength Lab . But, in general, youre looking at about 100 calories per mile if youre moving at a brisk pace.

Walking burns 100 calories a mile.

If you want to kick things up a notch, you can try walking up stairs or on a stair climber at the gym, which challenges your body even more, says Matheny. Again, there are a bunch of variables involved in this, but he says you can figure on burning about 200 calories a mile if youre walking up stairs.

So, if you walk one mile, youll burn about 100 calories. If you have the time to walk five to eight miles, youll probably burn 500 to 800 calories (about the same as running or biking for an hour ). And if you take it to the stairs, you're on a whole different, well, level.

Yes, you can actually get in shape by walking.

If youre not as fit as youd like to be, walking can help tremendously, says Matheny. He calls walking a great entry point for a lot of people and says its a key foundation to have in place for getting in shape. And yes, this counts as cardio. Any physical activity that elevates your heart rate above its normal resting rate can be considered cardio, Matheny says.

Walking is also really easy to do, he points out: You can do it anywhere, it's easy to get started, and theres no setup time. And, if you want to lose weight but are nervous about diving straight in to higher-impact activities, walking can help you lose body fat upfront, before you add in other types of fitness like running or spinning, Matheny says.

That said, how much walking helps you with your fitness depends on your baseline, Sklar says. If you regularly run half marathons, its unlikely that adding walking to the mix will do much to move your fitness forward. But if you tend to be pretty inactive, walking regularly can do a lot, he says-and then you can push it to the next level.

Check out how this woman lost 100 pounds by walking more:

If youre just starting out, aim for a low, attainable walking time that doesn't seem overwhelming, Sklar says. (This makes it more likely that youll continue, he says.) Then, over a period of a few weeks, increase the time and intensity of your walking-thatll help you keep seeing benefits over time, Sklar says.

Bottom line: If you're looking to add exercise to your routine, to help lose weight or up your cardio, walking is a totally viable, calorie-burning choice.