Crystal drive level approximation or typical value?

[shadewind]

I chose to use the TXC 7M series crystals for a recent project because they were small and seemed nice. When I chose them, I unfortunately didn't know know about the concept of drive level. The TXC 7M series specify a maximum drive level of 50 micro watts (I assume that's what 1 ~ 50 means). My fear is that this is too low for my design. I'm wondering I there is some approximation that can be done or if there is some typical value that is common. One of the devices is an STM32F micro and the other is an TI CC2500 RF transceiver.

I have read an STmicro app note about the subject but it only says how to measure it and I don't have the equipment to do that.

This is the datasheet for the crystal: http://www.txccrystal.com/images/pdf/7m.pdf