Usually you won't get more than some 22 Mbit/s actual throughput over 802.11.g, except when running some vendor-specific optimized setup (e.g. d-link router + d-link adapter, or asus-to-asus).

(wikipedia actually claims just 19 Mbit/s as average throughput: http://en.wikipedia.org/wiki/IEEE_802.11#802.11g)

Divide by 8 to get Mbytes per second.