How to calculate Rule of 72
Years to double = 72 / annual return rate.
Photo: Maxim Hopman on Unsplash
What this calculator computes
| Topic | Rule of 72 |
| Category | Investing & FIRE |
| Inputs | Contribution, return, time horizon, inflation |
| Output | Future value, withdrawal amount, retirement age |
| Math model | Compound growth with inflation deflation |
| Best for | Long horizon planning and retirement targets |
| Cost | Free, no login, in browser |
Step by step
Open Rule of 72 Calculator
Visit /tools/rule-of-72-calculator in any modern browser. The tool loads instantly and runs entirely on your device, so no inputs are transmitted to a server.
Gather your inputs
Have your contribution, return, time horizon, inflation ready. Accuracy on the output depends entirely on the quality of these numbers. If a value is uncertain, use the most realistic figure rather than rounding aggressively.
Enter the values
Fill each field in turn. Rule of 72 Calculator validates ranges as you type, so an obvious typo (for example a negative balance where one cannot exist) will flag immediately.
Read the result
The output is a rule of 72 result, derived from the inputs above, computed using compound growth with inflation deflation. Treat it as a precise answer to the question you posed, not an approximation.
Verify and compare
Re-run the calculation with a slightly different input to test sensitivity. For deeper comparison against another approach, see related tools in the Investing & FIRE hub or pick a related rule of 72 tool below.
When to use Rule of 72 Calculator
- Projecting a portfolio value at a future date
- Stress testing a withdrawal plan in retirement
- Comparing two contribution rates over decades
Frequently asked questions
What does Rule of 72 Calculator compute?
Rule of 72 Calculator computes a rule of 72 result, derived from the inputs above from contribution, return, time horizon, inflation, using compound growth with inflation deflation.
Is Rule of 72 Calculator free?
Yes. It is free, runs in your browser, requires no login, and does not transmit your inputs to any server.
What inputs do I need to use Rule of 72 Calculator?
You need contribution, return, time horizon, inflation. Accuracy depends entirely on the inputs you provide.
When should I use Rule of 72 Calculator?
Use it when your task is rule of 72 estimate and decision support and you need a quick, deterministic answer for a rule of 72 question.
Where can I find related tools?
Browse the full Investing & FIRE category for tools that share the same inputs or solve adjacent problems.
Keep exploring
- Open Rule of 72 Calculator
- Browse the Investing & FIRE category hub
- See comparison pages that include this tool on the compare index