A six-figure salary may once have been considered the benchmark of a comfortable lifestyle in the US.

But a new report suggests that in 15 major US cities, where the cost of living is particularly high, an annual $100,000 income is only enough to qualify as 'lower middle class'.

To put that in plain terms, earning six figures in these areas means you are among the poorest 40 per cent - and fail to meet the definition of middle class.

In three of the priciest cities - Arlington, San Francisco and San Jose - earning $150,000 a year is not even enough to move from 'lower middle class' and considered fully middle class. See definitions in box below.

The findings, from personal finance website GoBankingRates, lay bare how much rampant inflation is stretching even high-income families. 

Crippling rises to the cost of groceries, housing, childcare and transport have hit the whole of America, and some areas more than others.

Arlington in Virginia came out as the most expensive city, with households need at least $91,591 to be considered 'lower middle class'. Not until they reach $152,652 would they qualify as middle class. 

They would require even more to reach the mid-middle class and upper middle-class brackets.

The cost-of-living in the city is 41 percent higher than the national average and 121 percent higher if you focus only on housing, researchers said. 

Financial advisor Rodney Griffin said: 'Clients I work with in Arlington are seeing that impact with the cost of housing, transportation, healthcare, education and general lifestyle.

'While $150,000 may be a comfortable salary in some places, high demand from many people with comparative salaries can create an increased cost of living.'