Knowing the available throughput of the IEEE 802.11 link is highly beneficial. One use case of such information is the selection of an Access Point (AP) that will provide highest throughput. In this paper, we present a scheme for non-intrusive estimation of expected throughput of an 802.11 device. The proposed scheme does not require any aid from the infrastructure (e.g., AP) and does not create any additional traffic overhead (e.g., probe traffic). Our scheme relies on passive sniffing of the ongoing traffic for short duration (typically less than a second). Via sniffing, we obtain necessary parameters for throughput estimation, such as the collision probability. We have implemented our scheme in Linux system and Android smartphone. Experimental evaluation shows that our scheme accurately estimates expected throughput in various experiment settings.