Dave Ramsey's 15% rule suggests that you should invest 15% of your household income into tax-advantaged retirement accounts like 401(k)s and IRAs. This is after you've paid off all non-mortgage debt and have an emergency fund of 3-6 months of expenses.

Dave Ramsey uses a 12% average annual return in his calculations based on the historical performance of the stock market over the long term. While individual years may vary significantly, the S&P 500 has averaged around 10-12% returns over many decades when dividends are reinvested.

Dave Ramsey recommends investing in growth stock mutual funds across four categories: growth, growth and income, aggressive growth, and international. He suggests putting 25% of your retirement investments in each of these four types of funds for proper diversification.

Dave Ramsey emphasizes the importance of starting to save for retirement as early as possible. Thanks to the power of compound interest, even small investments made early can grow significantly over time. Ideally, you should begin saving in your 20s, but it's never too late to start.

The amount needed for a comfortable retirement varies based on your lifestyle, location, and expenses. Dave Ramsey generally recommends having enough savings to replace 80-85% of your pre-retirement income. This calculator helps you determine the specific amount you'll need based on your personal circumstances.