About 125 km. Depending on the traffic, it's about a 2 hours drive. Take the N20 out of Limerick and take that road straight to Cork.
248 km or 154.1 mi
About 250Km/156miles. Avg 3 -4 hours in a car.
You can use Google Maps to "Get Directions" between the 2 locations: Driving distance is 199 km - about 3 hours 0 mins As the crow flies, it's 157 kilometers
Distance between Cork and Killarney is 54 miles.