The lower the ratio the harder it is for a company to pays its debt. As a general rule interest coverage ratio below 1.5 does not make a good investment. This would signal a company may be having trouble paying down its debt and could go into bankruptcy if times get hard.
If the ratio is below 1 that means currently the company is unable to pay its bills. Investing in a company like this would mean investing in a company that is losing money.
