Two Lower Mainland grocery stores say they'll fix their scales after a CTV News investigation found they were shortchanging customers.

Both Sabzi Mandi on Main Street in Vancouver, and Apna Punjab grocery on King George in Surrey say they weren't intentionally overmeasuring by between five and 15 grams per purchase.

"It is not our purpose to steal -- why would we do that?" said Kuldeep Sekhon, the manager of Apna Punjab grocery.

CTV News tested Lower Mainland grocery stores for scale accuracy after obtaining government records that show that over the past five years, about one in twelve scales across the country were found to be mismeasuring.

We bought groceries at 20 different stores, buying everything from apples to chestnuts, and took those purchases to a scientific scale at the chemistry department at UBC.

Most goods passed -- but goods from the two different stores didn't measure up. We were overcharged by about 10 cents.

It doesn't seem like much, but scale experts say there's no reason every scale shouldn't be bang on.

"Scales are accurate," said Paul Mozsar from Pacific Industrial Scale. "If you're out five or ten grams, that's huge."

And it may be a little error each time -- but if a store is shortchanging it could add up to lots of money over many transactions, said Simon Fraser University marketing professor Lindsey Meredith.

"Do the math," he said. "You're not talking about a few pennies here, you're talking about hundreds of thousands of dollars."

The government records show that in the past even the single errors have been enormous. In 2005, the Sabzi Mandi store was found shortchanging customers by 22 per cent.

At Richmond BBQ, if a customer bought four pounds of meat the scale would read that they would purchase 15.

And it's not just the little stores. The Oakridge Safeway didn't fix its scales three times after failing inspections -- and in 2006 one scale was found to be off by 22 per cent.

The scales that the government tested were fixed by the inspectors, and everyone contacted by CTV said they had since fixed their scales.

On Dunbar, government inspectors gave Stong's grocery a clean bill of health in every inspection.

"We want to make sure the customers are getting what they pay for," Manager Lim Ng said.

With a report from CTV British Columbia's Jon Woodward