We propose a new technique to estimate the bandwidth available to wireless nodes and by extension on one-hop links in IEEE 802.11-based ad hoc networks. Our technique exploits the fact that a node can estimate the channel occupancy by monitoring its environment. It provides a non-intrusive estimation meaning that it does not generate any additional traffic to perform the evaluation. We show by simulations that our technique provides an accurate estimation of the available bandwidth on wireless links in many ad hoc configurations. However, we present also a configuration in which this technique does not give accurate estimations and propose a modification of our estimator enhancing its precision in that case.