A full-time stay-at-home mother would earn $134,121 a year if paid for all her work, an amount similar to a top U.S. ad executive, a marketing director or a judge, according to a study released Wednesday.

A mother who works outside the home would earn an extra $85,876 annually on top of her actual wages for the work she does at home, according to the study by Waltham, Massachusetts-based compensation experts Salary.com.

To reach the projected pay figures, the survey calculated the earning power of the 10 jobs respondents said most closely comprise a mother's role -- housekeeper, day-care teacher, cook, computer operator, laundry machine operator, janitor, facilities manager, van driver, chief executive and psychologist.

"You can't put a dollar value on it. It's worth a lot more," said Kristen Krauss, 35, as she hurriedly packed her four children, all aged under 8, into a minivan in New York while searching frantically for her keys. "Just look at me."

Employed mothers reported spending on average 44 hours a week at their outside job and 49.8 hours at their home job, while the stay-at-home mother worked 91.6 hours a week, it showed.

An estimated 5.6 million women in the United States are stay-at-home mothers with children under age 15, according to the most recent U.S. Census Bureau data.

NOT 'JUST A MOM'

"It's good to acknowledge the job that's being done, and that it's not that these women are settling for 'just a mom,'" said Bill Coleman, senior vice president of compensation at Salary.com. "They are actually doing an awful lot."

According to the U.S. Bureau of Labor Statistics, some 26 million women with children under age 18 work in the nation's paid labor force.

Both employed and stay-at-home mothers said the lowest-paying job of housekeeper was their most common role, with employed mothers working 7.2 hours a week as housekeeper and stay-at-home mothers working 22.1 hours in that role.

"Every husband I've ever spoken to said, 'I'm keeping my job. You keep yours.' It's a tough one," said Gillian Forrest, 39, a stay-at-home mother of 22-month-old Alex in New York. "I don't know if you could put a dollar amount on it but it would be nice to get something."

To compile its study, Salary.com surveyed about 400 mothers online over the last two months.

Salary.com offers a Web site (http://www.mom.salary.com) where mothers can calculate what they could be paid, based on how many children they have, where they live and other factors. The site will produce a printable document that looks like a paycheck, Coleman said.

"It's obviously not negotiable," he said.

On average, the mother who works outside the house earns a base pay of $62,798 for a 40-hour at-home work week and $23,078 in overtime; a stay-at-home mother earned a base pay of $45,697 and $88,424 in overtime, it said.

In a Salary.com study conducted last year, stay-at-home mothers earned $131,471. The potential earnings of mothers who work outside the home was not calculated in the previous study.