From today’s USA Today:

Darla Horn, 26, acknowledges she didn’t give much thought to the cost of college when she enrolled at State University of New York in Purchase. […] Because she didn’t qualify for financial aid, she took out student loans, graduating in 2005 with a double major in journalism and anthropology and more than $80,000 in debt.

That’s way too much debt for an anthro-journalist. But is it too much for an engineer? Is it too much for an actuary?

When I was buying a house, the rule of thumb was that you could afford a home three to four times your annual income. It feels like there should be an equivalent rule of thumb for how much you can spend on your education versus average salary of your studied profession. Or, hell, a web calculator.

In a few minutes of Googling, the closest I could find was this:

Don’t take out more student loans than what you expect to make in the first year. This rule of thumb puts a reasonable upper limit on how much in student loans you should take out, which is a good thing, but doesn’t paint the whole picture.

There are some jobs (like screenwriting) in which starting salary is almost impossible to predict, and others (like law) in which salary goes up quickly based on experience. But rules of thumb are helpful because they simplify things, and this one seems a good start.

By this measure, an actuary could take out about $50,000 in loans, while an electrical engineer could feel okay taking on $55,000 in debt. Darla, meanwhile, should have capped her loans at $33,000. (All salary estimates from PayScale.)

What often gets lost in these discussions is that relatively few students end up paying full freight. For four-year, private American universities, the average tuition discount rate for fall 2007 was 39.1%. The price on the sticker isn’t necessarily the price you pay.

But if you’re looking to study a low-paying field, do Future You a favor by being honest about the cost.