The fair place to meet is Phoenix, AZ — the city closest to the midpoint of Las Vegas and Salt Lake City. From the farther side that’s about 10 hr 36 min of driving.
Recommended midpoint
Phoenix, AZ
From Las Vegas
5 hr 22 min
256 mi to Phoenix
From Salt Lake City
10 hr 36 min
505 mi to Phoenix
Las Vegas has the shorter trip; the split is off by about 5 hr 14 min. The alternatives below can even it out. Las Vegas and Salt Lake City are about 363 miles apart.
Las Vegas and Salt Lake City are about 363 miles apart by road. Split the difference and you arrive near Phoenix, the city closest to the halfway point between them. That puts roughly 5 hr 22 min of driving on the Las Vegas side and 10 hr 36 min on the Salt Lake City side — the fairest single meeting point among the cities near the middle.
That's a half-day drive from each side, so Phoenix suits an overnight or a weekend rather than a quick coffee — long enough to want a reason to stay, short enough to drive.
If Phoenix doesn't have what you're after, Boise and Los Angeles are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Las Vegas and Salt Lake City.
Phoenix is the capital and most populous city of the U.S. state of Arizona. With over 1.6 million residents at the 2020 census, Phoenix is the fifth-most populous city in the United States and the most populous state capital. Read more →
Las Vegas, colloquially shortened to Vegas, is the most populous city in the U.S. state of Nevada and the county seat of Clark County. It is the 24th-most populous city in the United States, with 641,903 residents at the 2020 census. Read more →
Salt Lake City, often shortened to Salt Lake or SLC, is the capital and most populous city of the U.S. state of Utah. It is the county seat of Salt Lake County, the most populous county in the state. Read more →
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.
Estimates use straight-line distance and typical road speeds; real drive times vary with route and traffic.