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Corpus

Investment

Investment Corpus

The total accumulated pool of money built through investments over time. The corpus is the end goal of an investment plan ā€” for example, a retirement corpus is the total savings needed to sustain post-retirement expenses.

Definition

A corpus, in personal finance, is the total accumulated pool of money built through savings and investments toward a specific financial goal. The most common usage is a retirement corpus ā€” the total savings required to sustain a desired lifestyle throughout retirement without depleting the funds.

The concept of a corpus is goal-linked: you determine the corpus needed first (by working backward from your goal), then design an investment plan to reach it. SIP compounding over long periods is the primary tool for building a corpus.

The corpus represents the intersection of saving discipline, investment returns, time, and financial goals ā€” the "destination number" that personal financial planning is built around.

Formula

Required Retirement Corpus = Annual Expenses at Retirement / Sustainable Withdrawal Rate

SIP corpus projection:

Corpus = Monthly SIP Ɨ [(1 + r)^n āˆ’ 1] / r Ɨ (1 + r)

Where r = monthly return rate, n = total months of SIP

Target monthly SIP (to reach corpus C in n months):

Monthly SIP = C Ɨ r / [(1 + r)^n āˆ’ 1]

Worked Example

Kiran (age 30) wants a retirement corpus to support ā‚¹80,000/month in today's money, retiring at 60 (30-year investment horizon).

  1. Inflation-adjusted expense at 60 (6% inflation, 30 years): ā‚¹80,000 Ɨ (1.06)^30 = ā‚¹4,58,500/month = ā‚¹55 lakh/year
  2. Required corpus (4% withdrawal rate): ā‚¹55 lakh / 4% = ā‚¹13.75 crore
  3. Monthly SIP needed (12% expected return, 360 months): approximately ā‚¹32,000/month

If Kiran already has ā‚¹10 lakh saved, the existing corpus grows to ~ā‚¹3 crore in 30 years at 12%, reducing the SIP requirement to approximately ā‚¹25,000/month.

Use the SIP calculator and retirement calculator to model your specific numbers.

Key Things to Know

  • Inflation is the biggest enemy: Your corpus must be sized to beat inflation across a retirement of potentially 25ā€“30 years. A ā‚¹1 crore corpus that seems large today delivers only ā‚¹27 lakh of purchasing power in 25 years at 5% inflation. Always express your corpus target in future money, not today's money.
  • The power of early starting: Due to compounding, the last 10 years of a 30-year SIP period account for over 50% of the final corpus. Starting 5 years later requires nearly doubling the monthly SIP to reach the same corpus ā€” time is the most powerful variable.
  • Corpus depletion in retirement: A corpus is depleted if withdrawals exceed returns. An SWP from an equity-heavy portfolio at 4ā€“5% withdrawal rate can sustain the corpus indefinitely. Taking 8ā€“10% annually will deplete most portfolios within 15ā€“20 years.
  • Goal-based corpus: You may need multiple corpuses ā€” one for children's education, one for retirement, one for a house down payment. Treat each as a separate goal with its own timeline, SIP, and investment strategy rather than managing a single undifferentiated pool.
  • Corpus vs income: The corpus approach (building a lump sum and drawing from it) contrasts with the income approach (building assets that generate regular income ā€” rental property, NPS annuity, dividend stocks). Most retirees benefit from a blend of both.

Related Calculators

SIP Calculator ā†’Calculate your SIP returns instantly. Enter monthly investment, expected annual return, and time period to see total corpus, invested amount, and estimated gains.
Retirement Calculator ā†’Calculate your retirement corpus and monthly income in India. Enter current age, savings, monthly investment, returns and inflation to plan your retirement.
Savings Goal Calculator ā†’Calculate how much to invest monthly to reach any financial goal. Enter your target amount, existing savings, expected return, and time horizon.

Related Terms

SIPSystematic Investment PlanCAGRCompound Annual Growth RateInflationConsumer Price InflationNet WorthPersonal Net Worth
Frequently Asked Questions
How do I calculate my required retirement corpus?
The most widely used approach: (1) Calculate monthly expenses at retirement in today's money. (2) Inflate to retirement age using expected inflation. (3) Multiply by 12 to get annual expenses. (4) Divide by your expected withdrawal rate (4% is commonly used). Example: ā‚¹1 lakh/month today, retiring in 25 years at 6% inflation ā†’ ā‚¹4.3 lakh/month at retirement ā†’ ā‚¹51.6 lakh/year ā†’ Required corpus = ā‚¹51.6L / 4% = ā‚¹12.9 crore.
What is the 4% rule for corpus withdrawal?
The 4% rule states that if you withdraw 4% of your corpus in Year 1 of retirement and adjust for inflation each subsequent year, your corpus will last approximately 30 years (based on historical equity-bond portfolio returns). In India, with higher inflation, some planners use 3ā€“3.5% as a more conservative rate. The rule assumes a balanced portfolio (60% equity / 40% debt).
Should my retirement corpus include EPF and PPF?
Yes. Your retirement corpus includes all accumulated assets that will fund post-retirement expenses: EPF/EPS balance, PPF maturity value, NPS corpus (60% lump sum portion), mutual fund corpus, FDs, real estate rental income, and any other savings. However, the NPS annuity (40% mandatory) provides a separate monthly pension ā€” factor that in to reduce the lump sum corpus needed.
How does SIP help build corpus?
SIP is the primary corpus-building tool for most salaried individuals. Regular monthly investments compound over time ā€” the power of compounding means ā‚¹10,000/month for 30 years at 12% CAGR builds a corpus of approximately ā‚¹3.5 crore. The earlier you start, the less you need to invest monthly to reach the same corpus target.
What if I start corpus building late?
Starting late means you need to either invest significantly more each month, accept a lower corpus (and therefore lower retirement income), or retire later. For example, to build ā‚¹2 crore in 15 years at 12% return, you need ā‚¹30,000/month. The same corpus in 25 years requires only ā‚¹8,500/month. Starting early is by far the most effective lever.