For the first time, you can now test your lung capacity on the internet! Go to Lungtester, make sure your microphone is turned on and turn on the volume of your speakers too. Blow hard into your mic when you're being told to do so and wait for the results. The site says that u can then compare your results with the top athletes and your friends. Try it. And oh, make sure you brushed your teeth. You'll know what I mean when you try it out.
(Thanks Chloe Li)