72 ÷ rate = years to double
Common scenarios — click any to load it
The rate difference between these vehicles looks small on paper. Over 20–30 years, it's the difference between doubling once and doubling three times.
What the rule reveals
The math is simple. The insight is not.
Time is the variable that matters most
At 7%, $10,000 becomes $76,122 in 30 years — without adding a single dollar. That same $10,000 at 2.5% becomes $20,976. Same time. A 5% rate difference. A 3.6× outcome difference.
Inflation works against you the same way
At 3.5% inflation (roughly the 20-year average), your purchasing power halves in about 20 years. If your savings earn 2%, you're losing ground. The Rule of 72 applies to losses, not just gains.
The floor matters as much as the ceiling
IUL policies typically credit 0% in a down market — your cash value doesn't decrease even when the index drops. That protection matters in the Rule of 72 context: a 30% loss needs a 43% gain just to break even. Avoiding the loss keeps the compounding intact.
Doubling frequency compounds dramatically
At 7%, $100,000 doubles to $200k in ~10 years, to $400k in ~20 years, to $800k in ~30 years. Three doublings. At 2.5%, it doubles only once in 30 years. The number of doublings, not just the rate, is what separates outcomes.
What $10,000 grows to at different rates
Same starting point. Same time horizon. Very different outcomes.
| Years | 0.5% (savings) | 2.5% (HYSA) | 4% (bonds) | 7% (S&P avg) | 10% (nominal) |
|---|---|---|---|---|---|
| 5 | $10,253 | $11,314 | $12,167 | $14,026 | $16,105 |
| 10 | $10,511 | $12,801 | $14,802 | $19,672 | $25,937 |
| 15 | $10,778 | $14,483 | $18,009 | $27,590 | $41,772 |
| 20 | $11,049 | $16,386 | $21,911 | $38,697 | $67,275 |
| 25 | $11,328 | $18,539 | $26,658 | $54,274 | $108,347 |
| 30 | $11,614 | $20,976 | $32,434 | $76,123 | $174,494 |
Note: This is general educational information, not individualized investment, insurance, tax, or legal advice. Growth rates shown are hypothetical for illustration purposes only. Past market returns do not guarantee future performance. IUL and other insurance product illustrations depend on carrier, structure, and market conditions.