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Retirement Corpus Planner | How Much Do You Need?

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Retirement Corpus Planner: find your target retirement corpus and the monthly SIP needed to reach it, accounting for inflation. Free planner with year-by-year projection.

Last updated: October 2026 · Free · No sign-up required

“How much do I need to retire?” is the most important question in personal finance — and the answer is a number, not a feeling. This planner works backwards from your monthly expenses: it inflates them to your retirement date, computes the lump sum needed to fund them for life, and tells you the monthly SIP required today.

yrs

yrs

When you plan to stop working full-time.

$

Include everything: housing, food, transport, insurance, discretionary.

%

Long-term average; 5–6% is prudent in many economies.

%

Expected annual return while you are still saving.

%

Usually lower — capital preservation matters after retiring.

yrs

Plan conservatively — 85 is a common choice.


Results

Enter values above and click Calculate to see your retirement plan instantly.

How to use the Retirement Corpus Planner

Start from the lifestyle you want to protect, and let the planner work backwards to the savings rate you need.

  1. Enter your current age and planned retirement age. The gap between them is your accumulation window — every extra year of compounding helps enormously.
  2. Enter your current monthly expenses. Be honest and complete: include rent or EMI, groceries, transport, insurance, and discretionary spending. This is the lifestyle you want to sustain after retiring.
  3. Set expected inflation. In many economies, 5–6% long-term inflation is a prudent assumption; consumer prices roughly double every 12 years at 6%.
  4. Set your pre- and post-retirement returns. Before retirement you can typically take more risk (many planners use 10–12% for equity-heavy portfolios); after retirement, capital preservation matters more (6–8% is common).
  5. Enter your life expectancy and click Calculate. You will see your corpus target, the required monthly SIP, a 4%-rule comparison, and a year-by-year projection of your savings growth.

Formula & methodology

The planner works in four steps, from your expenses today to the SIP you need tomorrow:

Step 1 — Expenses at retirement. Your monthly expenses are inflated forward to your retirement date: Eret = E × (1 + f)T, where f is annual inflation and T is years until retirement. Multiply by 12 for the annual need.

Step 2 — The real return. Because your retirement withdrawals must keep rising with inflation, what matters is the return after inflation: rreal = (1 + rpost) / (1 + f) − 1.

Step 3 — Corpus needed. This is the present value of a growing annuity — a lump sum that funds inflation-adjusted withdrawals for your retirement years: Corpus = Annual need × [1 − (1 + rreal)−N] / rreal, where N is years in retirement. If the real return is zero, the corpus is simply annual need × years.

Step 4 — Monthly SIP required. Working backwards with the ordinary annuity formula: SIP = Corpus × i / [(1 + i)M − 1], where i is the monthly pre-retirement return and M is the number of months until retirement.

This method is more precise than the popular 4% rule (which says save 25× your annual expenses) because it accounts for your actual inflation outlook and the returns your corpus keeps earning after you retire — as the worked example below shows, the difference can be over a million dollars.

Worked example

Take a 30-year-old spending $3,000 per month, retiring at 60, expecting 6% inflation, assuming 12% pre-retirement and 8% post-retirement returns, living to 85:

Step 1: In 30 years, $3,000/month at 6% inflation becomes $3,000 × 1.0630 = $17,230.47/month, or $206,765.68 per year. That is the lifestyle cost you must fund.

Step 2: The real return after retirement is 1.08 / 1.06 − 1 = 1.89% per year.

Step 3: Funding $206,765.68/year of inflation-adjusted spending for 25 years at a 1.89% real return needs a corpus of $4,090,948.25.

Step 4: To build $4.09 million in 30 years at 12%, you need a monthly SIP of $1,170.53 starting today.

Compare the 4% rule: 25 × $206,765.68 = $5,169,142.06 — over a million dollars more. The 4% rule ignores the 1.89% real return your corpus keeps earning during retirement, so it overestimates what you need. The annuity method used here gives you credit for that growth, producing a smaller — but still safely funded — target.

The inflation impact is the real eye-opener: your $3,000 lifestyle costs $17,230 by age 60. Anyone planning with today’s prices and ignoring inflation will arrive at retirement with a fraction of what they need.

Frequently asked questions

What is the 4% rule, and how does it compare to this planner?
The 4% rule of thumb says you need 25 times your annual expenses saved, then withdraw 4% per year adjusted for inflation. It comes from US historical market research and assumes a specific stock/bond mix. This planner instead computes the exact present value of your inflation-adjusted withdrawals using your inflation and return assumptions — in our example it produced a $4.09M target versus the 4% rule’s $5.17M, because it credits the real return your money keeps earning after retirement.

What inflation rate should I assume?
For long horizons, 5–6% is prudent in many developing economies, while 2–3% suits the US and Western Europe. Check your country’s average CPI over the last 15–20 years and round up slightly — underestimating inflation is the most dangerous error in retirement planning, because the shortfall compounds over decades.

What returns are realistic to assume?
Be conservative. Many planners use 10–12% pre-retirement for equity-heavy portfolios and 6–8% post-retirement for conservative ones — but these are long-term averages, not guarantees, and your actual sequence of returns will vary. A useful stress test: rerun the planner with returns 2 points lower than your base case. If the required SIP is still affordable, your plan is robust.

What if I want to retire earlier or later?
Both levers are powerful. Retiring 5 years earlier shrinks your compounding window and extends the years your corpus must fund — the required SIP jumps sharply. Retiring 5 years later does the reverse twice over. Try moving the retirement age in the calculator: a few extra working years can cut the required monthly SIP by 20–30%.

Should I subtract expected pension or Social Security?
Yes, if you have reliable estimates. Compute your corpus need as above, then subtract the present value of those income streams — or simply reduce the monthly expense figure by the expected monthly pension in today’s money, since the planner’s inflation math handles the rest. Do not count on uncertain benefits.

How often should I recalculate my plan?
Once a year is enough, plus after any major life event — a raise, a new child, buying a home, or a market crash. Your required SIP drifts as expenses, age, and outlook change. Use the projection table: compare your actual balance against the projected path yearly and adjust if you fall behind.

Related Tools

“How much do I need to retire?” is the most important question in personal finance — and the answer is a number, not a feeling. This planner works backwards from your monthly expenses: it inflates them to your retirement date, computes the lump sum needed to fund them for life, and tells you the monthly SIP required today.

yrs
yrs

yrs
yrs

When you plan to stop working full-time.

$
$

Include everything: housing, food, transport, insurance, discretionary.

%
%

Long-term average; 5–6% is prudent in many economies.

%
%

Expected annual return while you are still saving.

%
%

Usually lower — capital preservation matters after retiring.

yrs
yrs

Plan conservatively — 85 is a common choice.

Results

Enter values above and click Calculate to see your retirement plan instantly.

How to use the Retirement Corpus Planner

Start from the lifestyle you want to protect, and let the planner work backwards to the savings rate you need.

  1. Enter your current age and planned retirement age. The gap between them is your accumulation window — every extra year of compounding helps enormously.
  2. Enter your current age and planned retirement age. The gap between them is your accumulation window — every extra year of compounding helps enormously.
  3. Enter your current monthly expenses. Be honest and complete: include rent or EMI, groceries, transport, insurance, and discretionary spending. This is the lifestyle you want to sustain after retiring.
  4. Enter your current monthly expenses. Be honest and complete: include rent or EMI, groceries, transport, insurance, and discretionary spending. This is the lifestyle you want to sustain after retiring.
  5. Set expected inflation. In many economies, 5–6% long-term inflation is a prudent assumption; consumer prices roughly double every 12 years at 6%.
  6. Set expected inflation. In many economies, 5–6% long-term inflation is a prudent assumption; consumer prices roughly double every 12 years at 6%.
  7. Set your pre- and post-retirement returns. Before retirement you can typically take more risk (many planners use 10–12% for equity-heavy portfolios); after retirement, capital preservation matters more (6–8% is common).
  8. Set your pre- and post-retirement returns. Before retirement you can typically take more risk (many planners use 10–12% for equity-heavy portfolios); after retirement, capital preservation matters more (6–8% is common).
  9. Enter your life expectancy and click Calculate. You will see your corpus target, the required monthly SIP, a 4%-rule comparison, and a year-by-year projection of your savings growth.
  10. Enter your life expectancy and click Calculate. You will see your corpus target, the required monthly SIP, a 4%-rule comparison, and a year-by-year projection of your savings growth.

Formula & methodology

The planner works in four steps, from your expenses today to the SIP you need tomorrow:

Step 1 — Expenses at retirement. Your monthly expenses are inflated forward to your retirement date: Eret = E × (1 + f)T, where f is annual inflation and T is years until retirement. Multiply by 12 for the annual need.

Step 2 — The real return. Because your retirement withdrawals must keep rising with inflation, what matters is the return after inflation: rreal = (1 + rpost) / (1 + f) − 1.

Step 3 — Corpus needed. This is the present value of a growing annuity — a lump sum that funds inflation-adjusted withdrawals for your retirement years: Corpus = Annual need × [1 − (1 + rreal)−N] / rreal, where N is years in retirement. If the real return is zero, the corpus is simply annual need × years.

Step 4 — Monthly SIP required. Working backwards with the ordinary annuity formula: SIP = Corpus × i / [(1 + i)M − 1], where i is the monthly pre-retirement return and M is the number of months until retirement.

This method is more precise than the popular 4% rule (which says save 25× your annual expenses) because it accounts for your actual inflation outlook and the returns your corpus keeps earning after you retire — as the worked example below shows, the difference can be over a million dollars.

Worked example

Take a 30-year-old spending $3,000 per month, retiring at 60, expecting 6% inflation, assuming 12% pre-retirement and 8% post-retirement returns, living to 85:

Take a 30-year-old spending $3,000 per month, retiring at 60, expecting 6% inflation, assuming 12% pre-retirement and 8% post- retirement returns, living to 85:

Step 1: In 30 years, $3,000/month at 6% inflation becomes $3,000 × 1.0630 = $17,230.47/month, or $206,765.68 per year. That is the lifestyle cost you must fund.

Step 2: The real return after retirement is 1.08 / 1.06 − 1 = 1.89% per year.

Step 2: The real return after retirement is 1.08 / 1.06 − 1 = 1.89% per year.

Step 3: Funding $206,765.68/year of inflation-adjusted spending for 25 years at a 1.89% real return needs a corpus of $4,090,948.25.

Step 4: To build $4.09 million in 30 years at 12%, you need a monthly SIP of $1,170.53 starting today.

Compare the 4% rule: 25 × $206,765.68 = $5,169,142.06 — over a million dollars more. The 4% rule ignores the 1.89% real return your corpus keeps earning during retirement, so it overestimates what you need. The annuity method used here gives you credit for that growth, producing a smaller — but still safely funded — target.

The inflation impact is the real eye-opener: your $3,000 lifestyle costs $17,230 by age 60. Anyone planning with today’s prices and ignoring inflation will arrive at retirement with a fraction of what they need.

Frequently asked questions

What is the 4% rule, and how does it compare to this planner?
The 4% rule of thumb says you need 25 times your annual expenses saved, then withdraw 4% per year adjusted for inflation. It comes from US historical market research and assumes a specific stock/bond mix. This planner instead computes the exact present value of your inflation-adjusted withdrawals using your inflation and return assumptions — in our example it produced a $4.09M target versus the 4% rule’s $5.17M, because it credits the real return your money keeps earning after retirement.
The 4% rule of thumb says you need 25 times your annual expenses saved, then withdraw 4% per year adjusted for inflation. It comes from US historical market research and assumes a specific stock/bond mix. This planner instead computes the exact present value of your inflation-adjusted withdrawals using your inflation and return assumptions — in our example it produced a $4.09M target versus the 4% rule’s $5.17M, because it credits the real return your money keeps earning after retirement.
What inflation rate should I assume?
For long horizons, 5–6% is prudent in many developing economies, while 2–3% suits the US and Western Europe. Check your country’s average CPI over the last 15–20 years and round up slightly — underestimating inflation is the most dangerous error in retirement planning, because the shortfall compounds over decades.
For long horizons, 5–6% is prudent in many developing economies, while 2–3% suits the US and Western Europe. Check your country’s average CPI over the last 15–20 years and round up slightly — underestimating inflation is the most dangerous error in retirement planning, because the shortfall compounds over decades.

What returns are realistic to assume?
Be conservative. Many planners use 10–12% pre-retirement for equity-heavy portfolios and 6–8% post-retirement for conservative ones — but these are long-term averages, not guarantees, and your actual sequence of returns will vary. A useful stress test: rerun the planner with returns 2 points lower than your base case. If the required SIP is still affordable, your plan is robust.
Be conservative. Many planners use 10–12% pre-retirement for equity-heavy portfolios and 6–8% post-retirement for conservative ones — but these are long-term averages, not guarantees, and your actual sequence of returns will vary. A useful stress test: rerun the planner with returns 2 points lower than your base case. If the required SIP is still affordable, your plan is robust.

What if I want to retire earlier or later?
Both levers are powerful. Retiring 5 years earlier shrinks your compounding window and extends the years your corpus must fund — the required SIP jumps sharply. Retiring 5 years later does the reverse twice over. Try moving the retirement age in the calculator: a few extra working years can cut the required monthly SIP by 20–30%.
Both levers are powerful. Retiring 5 years earlier shrinks your compounding window and extends the years your corpus must fund — the required SIP jumps sharply. Retiring 5 years later does the reverse twice over. Try moving the retirement age in the calculator: a few extra working years can cut the required monthly SIP by 20–30%.

Should I subtract expected pension or Social Security?
Yes, if you have reliable estimates. Compute your corpus need as above, then subtract the present value of those income streams — or simply reduce the monthly expense figure by the expected monthly pension in today’s money, since the planner’s inflation math handles the rest. Do not count on uncertain benefits.
Yes, if you have reliable estimates. Compute your corpus need as above, then subtract the present value of those income streams — or simply reduce the monthly expense figure by the expected monthly pension in today’s money, since the planner’s inflation math handles the rest. Do not count on uncertain benefits.

How often should I recalculate my plan?
Once a year is enough, plus after any major life event — a raise, a new child, buying a home, or a market crash. Your required SIP drifts as expenses, age, and outlook change. Use the projection table: compare your actual balance against the projected path yearly and adjust if you fall behind.
Once a year is enough, plus after any major life event — a raise, a new child, buying a home, or a market crash. Your required SIP drifts as expenses, age, and outlook change. Use the projection table: compare your actual balance against the projected path yearly and adjust if you fall behind.

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