weight lifting

You can if you want...

The best way is to get a heart rate monitor and wear it while working out. Those can tell you how many calories you burn throughout the workout. Other than that, it's simply a guess as to how many you think you burned lifting weights. There are so many factors that play into calorie loss by lifting that it's impossible to come up with a simple formula for the website to use... how much weight you use, how hard your pushing yourself, how long you rest between sets, how fast your heart rate gets and if you keep it that high between lifts or not... too much.

Get a heart rate monitor if you want to log the calories burned while lifting. (They aren't THAT expensive if you really want one)

I simply do 20 min on the elliptical and 20 min lifting... then I just log the elliptical time on MFP diary. Those numbers seem bloated compared to what the machine says I am burning... so I count the extra as my lifting calories burned. Plus, if you don't count them, you won't eat those calories back and you will automatically net less calories in your day without thinking about it! Calorie deficiency is the way to lose the weight, weight lifting is the way to stay toned... you are doing both, so that in itself is a moral booster!!