Cleanliness and comfort outweigh little luxuries like a solid breakfast, pool or in-room deluxe coffee machine for hotel guests at the end of their stay. That's according to the number crunching of online reservation site Hotels.com, which analysed 148 million comments from 5 million guest reviews to come up with what they call a “mathematical formula” for the perfect hotel stay F25 + C35 + B10 + P2 + Q + Br + D7 + S + W + 1/2H = “Hotel Perfection.”

The biggest takeaways – friendly staff is 10 times more important than free WiFi, while cleanliness and comfort are 35 times more important than a good breakfast, luxurious pool or deluxe coffeemaker in your room.