Compare four side-by-side savings scenarios with different rates, contributions, and timeframes.
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Each scenario runs the same future-value model (initial sum plus monthly contributions compounded monthly) at its own rate, and the calculator compares the four ending balances.
The spread between where your money sits now and where it could sit. If part of your savings is in a 0.5% account, move that scenario rate to a realistic high-yield rate and see the catch-up.
Over 20 years with monthly contributions, a 2-percentage-point spread can change the ending balance by tens of thousands of dollars. Time multiplies rate differences.