I travel every week for work. So most of the grocery shopping has fallen to my husband since we moved back to the states from Sweden.

Last month, I was going to stop at Costco to stock up on my way home from the airport. I consider myself a frugal shopper and dutifully read the Costco coupon book in preparation. I suggested to my husband that we buy coffee, detergent and toilet paper, but asked him if the prices were better at local stores or at this mega-store.

Now, my husband has had a career in banking and currency trading, and he can do advanced calculations in his head. But to check these prices, he said he needed a calculator and 15 minutes. I didn't understand why, until he came back with his scratch sheet full of numbers.

He explained that it's not enough anymore to just cut the coupon and compare products. You also have to pay attention to the size of the container. Apparently, manufacturers have been putting less food in the packages. Some call it hidden inflation. Instead of raising prices, some companies have just shrunk the product.

So look closely at your half-gallons of juice. They may be only 59 ounces. They used to be 64. When both sizes cost two for $6, be aware the smaller one is really 8 percent more expensive. Same for canned goods. A can of corn can be 15, 14.5 or 13.5 ounces.

In a recent week, my husband was in Sweden and I did all the food shopping. I was exhausted from the time I had had to spend comparing five or six different products when each had a different size and a corresponding different price.

I was literally stuck in the pasta aisle for 20 minutes comparing spaghetti prices. I started out looking at the special 99-cent package offered for the store-brand option. It looked like a bargain - until I picked it up and realized it wasn't enough spaghetti to feed two people. I then checked four other brands. All were different prices and different sizes.

Next came the orange juice aisle. That's where it got even more complicated. Not only were there different sizes (including the new "almost-a-half-gallon" half-gallons) and different prices, but we also had to pay attention to the ingredients. Brands that screamed "natural" or "100 percent Vitamin C" and were cheapest actually often had no real juice in them at all. Just flavoring and sugar.

I was afraid to look at the eggs, for fear that a dozen now actually only holds 11. Or maybe someone figured out how to sell them without the yolks for the same price.

I felt defeated. I had always thought I was fairly smart, yet all my education and experience couldn't seem to get me though a visit to the grocery story without losing out. Plus, I noticed at the checkout, some people were loaded with coupons to help cut their costs. I get the Sunday paper. I don't get that many coupons. Where did they come from?

Once I started talking to people about this, I realized there is help out there. This is some of the best advice I got:

• First, know your product prices. Often the two-for-one deal isn't a deal at all if the store raises the price before offering the deal. Such a product may be cheaper at another store, where it isn't "on sale."

• Second, bring your reading glasses and pay attention to the small per-weight price under the package price on the shelves. It is the real equalizer. Regardless of package size, it shows you what the cost is per pound, ounce, gallon or whatever the weight is and calculates it out for you.

• Finally, the last tip I got was from my hairdresser, Stephanie, at the Pinehurst Spa. She told me about one place for which I quickly developed great admiration. It is a website called moolasavingmom.com

This is a local mom from North Carolina who posts full spreadsheets every week on the main stores in our area, identifying what is on sale and what coupons are available. Often, she comes up with 100 percent savings on products. Amazing.

When my husband came back, I armed him with this new website and happily handed back the duties of deciding when a sale price is really a sale and when it is a ruse to dupe the many of us who don't go shopping with our calculators.

Marybeth Sandell recently moved to Pinehurst from Sweden with her husband and two daughters.