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Reviewed 2026-08
The Rule of 115 estimates years to triple money at a constant compound rate — a mnemonic, not a substitute for net and real returns.
Rule of 115 sits in the foundations family of this atlas: mechanisms first, products second, hype never.
Use the calculator for scenarios, then return to the section pages when you want the vocabulary behind the curve.
Formula115 ÷ rate %
OutputYears to 3×
SiblingRule of 72
Best forSteady rates
TrapFee-blind use
ToneEducational
Frequently asked questions
What is rule of 115 in one sentence?
The Rule of 115 estimates years to triple money at a constant compound rate — a mnemonic, not a substitute for net and real returns.
Is this financial advice?
No. Tool-Lifes pages are educational atlases. Decisions need your goals, constraints and, when appropriate, a licensed adviser.
Do I need a high return for compounding to matter?
Higher net rates help, but time and contributions often dominate — especially early. Costs and behaviour can erase a “good” rate.
How should I use the calculator?
Treat outputs as scenario sketches. Vary contribution, rate, fees and inflation to see which lever moves your goal date.
What about inflation?
Always ask whether a figure is nominal or real. A high nominal path can still lose purchasing power.
Are past returns a promise?
No. Illustrations use round teaching numbers. Markets, inflation and taxes change.
Where do fees show up?
In the net rate that compounds. Expense ratios, advice charges and spreads all reduce terminal wealth.
What page should I read next?
From foundations, continue to contributions-vs-rate or fee-drag; for behaviour, open consistency-habit or panic-selling.