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Rule of 72 calculator

Estimate how many years it takes to double your money at a given rate.

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Need Years to double? The Rule of 72 calculator derives it from Annual return (%) in one step. For instance, with Annual return (%) = 8 it returns Years to double = 9.

How to use it

  1. Enter your values: Annual return (%).
  2. Read the result instantly: Years to double.

Frequently asked questions

What does the Rule of 72 calculator actually compute?

It takes Annual return (%) and derives Years to double from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

A single value: Annual return (%). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Annual return (%) = 8, the calculator returns Years to double = 9. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Annual return (%) = 8.8 instead, Years to double goes from 9 to 8.182 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Annual return (%) = 7.2, Years to double comes out at 10. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Comparing two investments that pay at different times, deciding whether a project clears its cost of capital, and sanity-checking a valuation someone else produced.

What is the most common mistake?

Trusting a valuation without asking what share of it comes from the terminal value. Past 70%, the answer is an assumption about the distant future dressed up as a calculation.

How accurate is it, and what are the limits?

Estimate only — not financial advice.

What is the difference between the Rule of 72 calculator and the Index Fund Calculator?

This one returns Years to double; the Index Fund Calculator returns Future value and Total invested. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

SIP calculator is the closest one after this: Project the future value of a monthly investment plan with compound growth.

Further reading

All guides →
ExplainerThe Rule of 72, ExplainedThe rule of 72 estimates how long money takes to double: divide 72 by the interest rate. Here's why it works, when it's accurate, and how to flip it.ExplainerHow Does Compound Interest Work?Compound interest is interest earning interest. Here's the formula, a worked example, and why starting early beats saving more later.ComparisonSimple vs Compound Interest: What's the Difference?Simple interest grows in a straight line; compound interest snowballs. Here's how each works, a worked example, and which one you meet in real life.ExplainerWhat Is an Index Fund? How Passive Investing WorksAn index fund tracks a whole market instead of betting on winners. Learn how tracking works, why diversification and low fees matter, and how it stacks up against active funds.ExplainerWhat a 1 Percent Fee Costs Over 30 YearsA one-point difference in annual charges turns $75,063 into $57,435 on the same $10,000. The fee costs more than the sum invested — here is why compounding does that.ExplainerThe 4 Percent Rule: What It Actually ClaimsSpending $40,000 a year needs $1,000,000 at 4 percent and $1,333,333 at 3 percent. Where the number came from, what it measured, and the four objections that matter.