In an ideal environment, your mouse or keyboard can operate up to 30 feet (10 meters) away from the receiver in a clear line of sight.
If you're not getting this distance, try these suggestions:
Replace the batteries in your mouse or keyboard
Move devices that emit radio waves or could cause radio interference away from your work area (Examples: cell phones, radios, wireless routers, microwaves)
To determine if your environment is shortening your operating range, try using your device in a different environment to see if the distance improves. If it does, look for other possible sources of interference you can remove from your work area.