you are want RBX
you are want calculator (RBX) and convert rbx to usd.

This is a free and amazing tool
it's a powerful robuc and usd calculate for RBX.
This app very is simple
Please Note:
* " RBX calc free" is only to help gamer in calculating cost of the RBX
This app is NOT a cheat or hack to get free RBX in game