Hi jagb,
That is a difficult question to answer as it depends very much on the antenna design, transmit power, and also the operating environment.
Typically ANT is used in personal area networks where the required range is less than 10m.
Most of the ANT products I own will connect anywhere within the house. E.g. my FR70 in the utility room at the front of the house connects to my laptop in the dining room at the back of the house, so I leave my watch in my bag and the data uploads to Garmin Connect automatically.
Testing your product is the best way to find out the range.
Kat