The FIRE Calculator is a free tool that helps you calculate fire using the formula Future monthly expense grows with inflation; corpus = 25x annual expense (4% rule); SIP solves for that corpus.. Enter your values above and press Calculate to get corpus needed at retirement, monthly sip required instantly, with a full step-by-step breakdown.
What is the FIRE Calculator?
The fire calculator is a free online tool that helps you calculate fire quickly and accurately. It applies the standard formula Future monthly expense grows with inflation; corpus = 25x annual expense (4% rule); SIP solves for that corpus. to the values you enter and, when you press Calculate, displays the result together with a clear, step-by-step explanation of how the answer was reached.
How to use the FIRE Calculator
- Enter your age and target retirement age.
- Enter current monthly expenses.
- Enter inflation and expected return.
- See the corpus and monthly SIP needed.
Formula used
The fire calculator is based on this formula:
Future monthly expense grows with inflation; corpus = 25x annual expense (4% rule); SIP solves for that corpus.Each term in the formula corresponds to one of the inputs explained below. The calculator performs the arithmetic for you and shows every step so you can check the working by hand if you wish.
Worked example
Suppose you enter Age 30 to 60, 50000/month. The calculator works as follows:
| Inputs | Age 30 to 60, 50000/month |
|---|---|
| Working | Inflate expense, apply 4% rule, solve SIP |
| Result | Required corpus and SIP (illustrative) |
Step-by-step calculation
- Apply the formula:
Future monthly expense grows with inflation; corpus = 25x annual expense (4% rule); SIP solves for that corpus. - Substitute your values: Inflate expense, apply 4% rule, solve SIP
- Read the result: Required corpus and SIP (illustrative)
Inputs explained
- Current age (years) — the current age used in the calculation.
- Retirement age (years) — the retirement age used in the calculation.
- Current monthly expense — the current monthly expense used in the calculation.
- Inflation (%) — the inflation used in the calculation.
- Pre-retirement return (%) — the pre-retirement return used in the calculation.
Understanding your result
- Corpus needed at retirement — the calculated corpus needed at retirement.
- Monthly SIP required — the calculated monthly sip required.
Benefits and practical uses
The fire calculator saves time and removes the risk of manual errors when you need to calculate fire. It is useful for students, professionals and anyone who wants a fast, dependable answer. Results update the moment you press Calculate, work on any device, and can be copied or shared in a single click — and because the maths runs in your browser, your figures stay completely private.
Tips for an accurate result
- Keep all related inputs in the same units.
- Use the worked example above to confirm you are entering values in the right places.
- Review the assumptions below so the result fits your situation.
- Press Reset to clear everything and try a different scenario.
Common mistakes to avoid
- Entering values in the wrong unit (mismatched units give wrong answers).
- Leaving a required field empty — the calculator will ask you to fill it in.
- Confusing the annual rate with a monthly rate, or tenure in years with months.
- Treating the estimate as a guaranteed return — markets and rates vary.
Assumptions and limitations
- 4% safe-withdrawal rule.
- Constant inflation and return.
- Excludes existing savings and pensions.
Frequently asked questions
What is the 4% rule?
A guideline that you can withdraw about 4% of your retirement corpus each year, so the corpus is roughly 25x annual expenses.
How do I use the FIRE Calculator?
Enter your values in the fields, then press the Calculate button to see the result. Use Reset to clear the form and start again. Nothing is calculated until you click Calculate.
What formula does the FIRE Calculator use?
It uses the standard formula: Future monthly expense grows with inflation; corpus = 25x annual expense (4% rule); SIP solves for that corpus.. The full step-by-step working is shown with every result so you can verify it.
What information do I need to use the fire calculator?
You need: current age, retirement age, current monthly expense, inflation, pre-retirement return. Sensible example values are pre-filled so you can see how it works.
Is the FIRE Calculator free to use?
Yes. Every DigiToolkit calculator is completely free, with no sign-up, no login and no usage limits.
Does the FIRE Calculator work on mobile phones?
Yes. The calculator is mobile-first and works on phones, tablets and computers in any modern browser.
Do I need to install an app?
No. The fire calculator runs directly in your web browser — there is nothing to download or install.
Is my data private when I use this calculator?
Yes. All calculations run inside your browser. The numbers you enter are never uploaded to a server or shared with anyone.
How accurate is the FIRE Calculator?
It uses the generally accepted formula for fire and computes to several decimal places. Results are accurate for the assumptions listed on this page.
Can I copy or share my result?
Yes. After calculating, use the Copy button to copy the result, or Share to copy the page link.
Why is nothing showing until I press Calculate?
By design, the calculator only computes when you press Calculate, so you can finish entering all your values first. Press Reset any time to clear everything.
What units does the FIRE Calculator use?
It works with %, years. Keep your inputs in consistent units for an accurate result.