[patriciacorse007]

One estimate of cumulus cloud density is as a density of about 0.5 gram per cubic meter. A 1 cubic kilometer (km3) cloud contains 1 billion cubic meters. Doing the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud.

[alancalverd]

Assuming you mean kg/m³, that's still a very high cloud - about 20,000 ft. You might encounter cumulus at that height in Texas but it's about the top of a very big cumulonimbus in the UK!