AT&T today announced that its new shared data plans will be available starting Aug. 23. The new plans are not -- repeat, not -- mandatory. So if you have one of those grandfathered unlimited data plans now, you'll can still have it on Aug. 23. Here's the breakdown of what the plans will cost you:

Amount of data in plan Cost for data Cost for each device Base total
1GB $40 $45 $85
4GB $70 $40 $110
6GB $90 $35 $125
10GB $120 $30 $150
15GB $160 $30 $190
20GB $200 $30 $230

So, for example, if you had two smartphones on a 6-gigabyte plan, you'd pay $160 a month. Voice calls and text messaging -- as well as tethering -- are included.

AT&T's also rigged up a little tool that will help you figure out which of these shared data "buckets" would be right for you. (Hit the link below to check it out.)

Source: AT&T; Also: Shared data plan tool