Howard Miller does not state the altitude limit for accuracy of this unit. Generally, off-the-shelf "decorative" barometers are accurate to 5,000ft; accuracy wanes as altitude increases from there. For Weems & Plath barometers, the off-the-shelf models are claimed to be good to 6,000ft. So, for a non-barometer company, I backed off again in my guesstimation.