Most consumers know what they're getting if they request a king-sized bed at a hotel or a grande latte at Starbucks. But that's not so in the world of car rentals.

At Avis, a Chevrolet Cruze is deemed intermediate or mid-sized, although the manufacturer calls it a compact. A Nissan Versa rented from Hertz is considered a compact, but its maker says it falls in the subcompact category. And Enterprise lists a Nissan Altima as full-size, though Nissan begs to differ, calling it a mid-sized car.

A scan of several compact, mid-sized and full-sized rental cars reveals that in many cases, the size assigned by the three major rental companies differs from that of the manufacturer, often with a smaller vehicle being listed in a larger category.

And many business travelers, who rely on rental vehicles to get them around while they're on the road, find the sizing disparities irritating.

"There is no relationship between what the general public thinks a mid-size or compact is vs. the car-rental companies,'' says Jay Hibbard, a member of USA TODAY's Road Warriors panel of frequent travelers, who is a vice president of government relations and based in Portland, Maine. "When a (Toyota) Corolla . . . is considered mid-sized, there is a mismatch in thinking.''

"Compact, mid-size, these seem like terms that would have a standardized meaning,'' Christine Sarkis, senior editor at SmarterTravel, said in an email.  "But in the car rental industry, they often don’t. A car that one agency might classify as a compact might be another company’s mid-size.''

Christy Cavallini, a spokeswoman for Enterprise Holdings, says many factors contribute to why a rental car company may fit cars into a different category than the vehicle's manufacturer.

"Car classes are determined by how many people the vehicle seats, how much luggage can fit in the trunk, cost of vehicle, equipment and technology upgrades,'' she says.  "A manufacturer may categorize a $120,000, a $40,000 and a $25,000 vehicle as intermediate cars, but their costs and equipment are quite different."

Hertz Global Holdings spokesman Bill Masterson adds that because rental car companies are carrying such a variety of vehicles, from so many different companies, they must make size categories "relative among those makes and models.''

And, says Cavallini, "we are very clear on our website about how many people and how much luggage each vehicle class accommodates, so customers know exactly what to expect. ... We want to make our customers happy, so if the vehicle doesn’t meet a customer’s expectations, we will give them a vehicle that does.''

But larger cars generally cost more to rent. And to some corporate trekkers, whether traveling with a group, or juggling laptops and luggage, when smaller vehicles are categorized as being larger, they feel misled.

"Candidly, it's a bit dishonest,'' says Road Warrior David Buckner, a New York City-based corporate consultant and executive trainer. "Ordering a full-size car only to find the same car you rented last year as a mid-size car (is now) at the new full-size rate is aggravating and makes the consumer question the integrity of the rental agency. ''

And vehicle size, he says, does matter.

"I travel . . .. with materials, tools and heavy bags that need trunk space,'' he says. "Paying more for a Chevy Impala to assure I have sufficient space only to arrive and be told a Chevy Malibu is now a full size car is aggravating, especially when I arrive after midnight and all of the exchange booths are closed.''

Road Warrior Greg Adamson, a sales manager in Phoenix, says that it "gets ridiculous with what the rental car companies consider as a mid-size. I'm in rental cars every week, and it's always a challenge, even for the veteran traveler. I can only imagine the frustration for those traveling once or twice a year.''

David Frisbie, an author and speaker based in San Diego, says that he has seen some of those confused travelers first hand.

"The consumer has a very clear understanding of terms such as mid-size or full-size,'' says Frisbie. "As I arrive to pick up a rental vehicle, I often discover unhappy people who are hoping to change the size of the vehicle they reserved because it is not large enough for their needs."

Marilyn Repinski, a Road Warrior who works in consulting and lives in Gig Harbor, Wash., says that because of the mismatched sizing, "I always ask in advance about the make and models that are considered in this category so I don't over- or under-reserve for my need on a particular trip.''

And Clarissa Cervantes, a Los Angeles-based photographer, says "actual full-size cars are now 'premium' or 'luxury' ...  not to mention that according to their availability, stocks and regional areas, those standards can change dramatically. One of the best things to do as consumers is to shop around, use coupons, make sure you are getting the best price available for each category, and if you are not satisfied, take the time and negotiate something better at the pick-up stand.”

Like Enterprise and Hertz, which say that customers can view the car possibilities and dimensions clearly when booking a rental on their websites, Avis Budget Group spokeswoman Alice Pereira says customers can find facts ranging from the number of people a vehicle holds to fuel efficiency online. "Once the traveler clicks 'reserve,' they are able to see the other makes and models included in the car class,'' she says.

Sarkis, at Smartertravel, says that despite the category differences, rental agencies can't necessarily be accused of false advertising.

"This is certainly confusing, but not necessarily misleading,'' she says. Still, "it’s a good reminder that you can’t take terms like compact or mid-size at face value. ... Use them as a general guide, then dig a bit deeper to understand what a car-size category actually gets you with a particular company. Remember that size is only one measure. Features like cruise control are also often tied to car class."

And if you're still perplexed, she says, consider renting a convertible, an SUV or a truck.  "In car classes like these,'' she says, "there’s not much room for interpretation, so you’re more likely to get what you’re expecting.''

Comparing rental car sizes

AVIS                      

CAR                RENTAL CATEGORY         VS. THE MANUFACTURER'S 

Fiat 500                    Compact                                     Subcompact

Chevrolet Cruze    Intermediate                              Compact

Chevrolet Malibu     Full-Size                                   Mid-Size  

Hertz

Nissan Versa                      Compact                      Subcompact

VW Jetta                           Intermediate                   Compact

Chrysler  200                     Full-Size                       Mid-Size

Enterprise

Chevrolet Sonic    Compact    Subcompact

Nissan Sentra       Intermediate     Compact

Nissan Altima            Full-size      Mid-Size

Source: Avis Budget Group, Hertz Global Holdings, Enterprise Holdings and USA Today Research