Just tried out the site.

The site looks professional and I found it very easy to use. I just tried with one of my addresses and all the calculations seem to be correct.

Something you guys might want to look into is to add the ability for users to enter a hd wallet xpub key instead of single addresses. It would be far easier to just copy/past a xpub key instead of adding every single address.

With HD wallets that can be a real pain as most HD wallets use a new address for every transaction meaning that you might end up with a load of addresses by the end of the year. Would be far easier to just enter the xpub key then instead of trying to copy/past every single address.