Home bakers have stirred up Libby's Famous Pumpkin Pies since 1950, according to Nestle's Web site, but over time the amount of pumpkin in those pies may have slipped. While the company's recipe now includes a 15-ounce can of pumpkin, the online sharing site Cooks.com has a version calling for a 16-ounce can of Libby's.

Is this kind of thing going to ruin a cook's day? Not likely, said Vanessa Johnson, test kitchen director for Cooking Light magazine. Her staff regularly sees sizes of cans, boxes and bags change -- and they cope. "We have this happen all the time," she said.

Old recipe books may be among the few places consumers can find documentation that canned corn used to come in larger quantities and apricot halves in bigger amounts. Companies would really rather not advertise that you're paying the same but getting less.

"It's very difficult for companies to put on the package, 'Look, we've made it smaller for you,' " noted Todd Hale, senior vice president of consumer and shopper insights for the Nielsen Co.

Package tinkering has been around a long time. But in the past couple of years, shocking increases in commodity and fuel costs following a long stretch of stable prices have set off a wave of packaging overhauls touching goods on shelves all over the grocery store.

Kellogg Co. recently rolled out smaller boxes of cereals such as Froot Loops, Cocoa Krispies and Corn Pops. The maker of Dreyer's and Edy's ice cream shrunk its cartons from 1.75 quarts to 1.5 quarts. O'Hara grocer Giant Eagle confirmed it has changed package sizes on some of its private label goods to balance cost issues with the need to compete on value with national brands.

Even the move to laundry concentrates pitched as way to be "green friendly" come, in part, as a response to rising costs, said Mr. Hale. Transporting heavy goods burns up fuel. He noted a new Arm & Hammer Essentials cleaner is designed so consumers add the water at home. "I think of that in terms of downsizing from a shipping point of view," he said.

It's easier to market some packaging changes than others. A popular way to ease customers through the cost issues is by trying new, less expensive materials or less bulky designs. Those can open up opportunities to tinker with content weight or the marketing message. Sometimes a new, improved version might require a second look to see what's really different.

"Now when I look at things and they are cheaper, I do tend to check the sizes," said J. Lynne Brown, a professor of food science at Penn State University who noticed the less expensive container of orange juice she'd picked up ran out a day earlier than the old one.

Those in the restaurant business have found ways to turn smaller servings into an asset. Eat'n Park's new smaller portions menu and T.G.I. Friday's Right Portion, Right Price offerings can be seen as a way to save money and perhaps cut calories.

But just downsizing the amount inside a box is a tough sell, said new product consultant Marilyn Raymond, of the Arbor Strategy Group in Ann Arbor, Mich.. "I wonder how consumers would react to: 'Introducing our new priced-right size -- smaller size to help manage overall budget!' "

Consumers faced with increasing financial pressures already may have developed their own systems for managing their budgets. Mr. Hale has heard stories of people adding a half-gallon of water to a gallon of milk as a way of stretching that increasingly expensive liquid.

Of course, that's their own choice. A discreet corporate package downsizing may be a different matter.

With no easy way to explain such moves to shoppers without drawing attention to the fact that their money is buying less, companies tend to just do it and answer questions later. That can leave a bad taste for shoppers who happen to stumble across changes, as proven by the complaints posted on blogs, chat boards and shopping Web sites.

An explanation, even delayed, may help. "We have been heartened by the number of consumers who, after initially expressing concern about the carton size change and asking us to explain the factors that led to our decision, have actually recontacted Dreyer's/Edy's to express their understanding and commitment to our brand," wrote Kim Goeller-Johnson, a consumer communications staffer at the ice cream maker, in an e-mail response.

Eventually, consumers get used to the new sizes, said Ms. Raymond, citing the example of coffee that once came in 16-ounce cans but has been selling in 12-ounce sizes and appears to be heading toward 10-ounce containers. "Truthfully, I think that most appreciate having a price point that doesn't go up too high. Something like coffee has to stay under $10."

There are alternatives to putting less coffee in the can or chocolate in the candy bar, and just about every variation possible is being used by some manufacturer at the moment.

Companies sometimes try to absorb the expense for a while, although that cuts into profit margins. They can also raise prices and hope the extra money exceeds sales lost to customers who don't want to pay that much, said Mr. Hale.

The Hershey Co. in mid-August announced plans to raise prices an average 10 percent across domestic product lines. Officials said market prices for cocoa, corn sweeteners, sugar and peanuts had risen 20 percent to 45 percent since the beginning of the year.

"Consumers are likely to see higher every day and promotional retail prices as we implement the price increase and, as a result, we expect volume in the fourth quarter and next year to be lower than previously estimated," said David J. West, president and chief executive officer, in the announcement.

Del Monte Foods Co. has raised prices on everything from tomatoes to fruit to pet food this year and the company is considering yet another increase for its pet products.

While packages may have shrunk in the past, that's not been the case lately, said company spokeswoman Mary G. Sestric. "The vast majority of our products have not been impacted in terms of packaging size," she said in an e-mail.

For those who still have recipe books from 10, 20, even 30 years ago, that may not matter. A blogger at justshootmenow.wordpress.com offered a rant against morphing package sizes earlier this year, complaining manufacturers afraid to raise prices were messing up recipes like a corn casserole that called for 16-ounce cans of creamed corn and sweet corn.

In conclusion, the rant called for readers to get off their kitchen stools and protest. "Let's all meet at the Del Monte offices and throw stewed tomatoes at them. From the 15-ounce cans."