With the recent makeover of Gmail homepage, how much bandwidth did Google saved? Maybe around 42,500,000,000 bytes per day, at least. Google cited that they removed 250 words in the process and that would be more than 250 bytes. Anyway, 250 bytes will be used for calculation.
At the same time Google has more than 170 million users and most Google GMail users are active. Thus, 170,000,000 * 250 would equals 42,500,000,000 bytes. Figures not right? Then present your calculation.
Anyway, with modern computers that big figures are actually small but in the long run, it will matter.
Moving on to the number of GMail users, there is no actual figures, just estimates.
1. Number of Gmail Users as of March 2010: 170 million users. Source: numberof.net
2. Number of GMail Users as of February 2008: 91.6 million users. Source: email-marketing-reports.com
3. Number of GMail Users as of February 2007: 51 million users. Source: TechCrunch