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Mutual fund calculators · Retirement accumulation and spending

Retirement SIP Calculator

Created by Arunangshu DasReviewed

Estimate the corpus and fixed monthly investment needed to fund a supplied retirement spending gap.

Use separate accumulation and retirement assumptions, and see how existing savings offset the required corpus.

Retirement spending and accumulation

Enter the spending gap after any income you choose to include. Withdrawals occur at each retirement month end.

Formatting only. The calculator performs no currency conversion.

Monthly amount to fund retirement

Enter spending and funding assumptions or load the worked example.

The payable contribution uses 0.01 increments in nominal money. The corpus funds the modeled withdrawals with zero planned terminal estate.

Understand what drives the projection

Follow the spending projection, corpus calculation and monthly contribution check.

Read the complete Retirement SIP guide

Formula and methodology

Required corpus = sum of retirement withdrawals discounted to retirement.

Convert effective annual assumptions to monthly factors. Let p be the price factor, f the retirement growth factor, n months until retirement and m retirement months. A gap G in opening purchasing power gives a withdrawal G × p^(n+k) at retirement month k. Discount by f^k for k from 1 to m and sum. Fund the resulting corpus with projected existing savings and fixed monthly contributions.

Definitions

A retirement SIP model first values a user-supplied monthly spending gap across retirement, then estimates the fixed nominal contribution needed to build that corpus before retirement.

Verified worked examples

With a monthly spending gap of 100, three months of retirement and all rates zero, the required corpus is 300. Existing savings of 100 leave a gap of 200. Over three accumulation months, the mathematical contribution is 200/3. A payment of 66.67 ends at 300.01. A payment of 66.66 falls short at 299.98.

Interpretation

The required corpus is in retirement-date money. The first withdrawal occurs one month later and uses that checkpoint’s money. The rounded-payment surplus is an accumulation result and does not increase the spending schedule.

Inputs and interpretation

Enter the gap in opening purchasing power, existing savings, months before and during retirement, and separate effective annual accumulation, retirement and inflation rates. Choose beginning or end accumulation payments. Retirement withdrawals are at month end.

Assumptions and limitations

Use whole equal months and a constant price assumption. Withdrawals begin after one retirement month and the corpus targets zero terminal estate. Accumulation contributions are fixed nominal amounts. Zero retirement months means no withdrawals.

Supported domain and common mistakes

Each horizon is from 0 to 1,200 months. Input amounts are 0 through 10^12 and rates are above −100% through 100%. Decimal inputs support 12 fractional places. The model rejects unsupported payments, monetary results above 10^30 and unresolved funding thresholds.

Keep opening purchasing power, retirement-date money and withdrawal-date money distinct. Use the gap you want funded after any income you considered. Avoid applying inflation twice or assuming that returns are constant outside the model.

Frequently asked questions

How much monthly SIP do I need for retirement?
The calculation first values the modeled retirement withdrawals. It then subtracts the projected existing savings and solves the monthly payment needed to cover a positive gap.
What is the monthly spending gap?
It is the spending you want this portfolio to fund in opening purchasing power. Account for any outside income you choose before entering it.
Why are there two return inputs?
Accumulation grows your savings before retirement. The retirement rate discounts withdrawals and represents how the remaining balance grows after retirement.
When does the first withdrawal happen?
At the end of the first retirement month. Its amount reflects prices through that checkpoint.
What happens if I have no months before retirement?
The existing balance either covers the modeled corpus or leaves an immediate funding gap. The model schedules no monthly contribution.
Does this estimate my pension benefit?
No. It uses the spending gap you enter and does not estimate any pension, public benefit or tax outcome.

Sources and educational scope

Educational constant-rate projection. It excludes dates, lifespan, pensions, tax, fees, FX, account rules and variable returns. It does not determine sustainable income or provide personalized investment advice.

Reviewed . AI-assisted content under operator editorial responsibility. No independent expert financial review is claimed.

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