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There is no answer as it's dependent on both the phone and the other Bluetooth device.

A cheap Bluetooth headset signal can be blocked by your body. While a good one can be 30 ft away and still work.
 
older bluetooth headsets used to be mostly Class II, with a 30ft/10m range. but i think the 5S may be a Class I device with a possible 100m range. but it all depends on surroundings, power and interference.
 
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