Use this calculator to see how contributions to your 401(k) plan can add up over time. Enter the amount for a monthly contribution or a one-time windfall, and see how it will grow based on the amount of time until you retire and an assumed rate of return. What if you just contributed an extra $20 per month to your savings account or retirement account? How much of a difference might that make 30 years from now? When you factor in the power of compound interest, the answer may surprise you.  See how skipping a few lattes each week might help you substantially increasing your savings or retirement nest egg.

A good rule of thumb for choosing a rate of return is to estimate 8% if you're 5 years or less from retirement, or 11% if you're any further from retiring.