Deciding whether you need life insurance is pretty easy. Figuring out how much you need is not easy at all.
Many people just pluck some figure out of the air that seems reasonable and settle on that.
Some lean on an old rule of thumb that says you need four to five times your annual income. That's better, but in this day and age you really should approach the problem more scientifically. What would it take to pay off the mortgage or other debt, and continue funding the children's college funds. Don't forget about funeral expenses, probate costs and, depending on the size of your estate, estate taxes . Basically you will need to estimate the income your dependents would need to maintain their standard of living if you were to die tomorrow.