Mine is zoomed uth for 30-40 gallon take approx 8x11 inches and it gets upwards of 115-130 without a thermostat regulating it. My thermometer has my abient temp at approx 92 on the hot side. I had a Burmese come into my work with burns because the owner thought the uth wasn't getting above 92. They didn't have a thermostat. upon mine and the vets recommendation they took a temp of the glass above the uth and it was at 120 farenheit. I would use a probe to check the temp as it is better safe than sorry. What type of thermostat do you have?