Retirement Planning Calculator — Corpus & Required Monthly SIP

Retirement planning has three numbers: how much you’ll need at retirement (corpus), how much you must save each month to build that corpus, and how to draw it down so it lasts. Most calculators only do one of these. This one does all three — adjusted for inflation, with separate pre- and post-retirement return assumptions.

Retirement Planning Calculator

Find out exactly how much you need to retire — and how much to save monthly to get there.

$
Inflation5.00%
Pre-retire11.00%
Post-retire7.00%
$

Your Retirement Plan

Required Retirement Corpus–
Future Monthly Expenses–
Required Monthly SIP–
Years to Retirement–
Years in Retirement–

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Why Retirement Numbers Look So Big

Two compounding forces work against you. First, inflation — at 5% inflation, $3,000 in monthly expenses today becomes $13,000 in 30 years. Second, retirement length — modern retirees live 20–30 years past retirement, so you need a corpus that funds 240–360 months of inflation-adjusted living.

The good news: compounding works for you on the savings side. A $300/month SIP for 30 years at 11% becomes ≈ $815,000 — without you ever earning more than your starting salary.

The Math (Two-Step)

Future Expenses = Current × (1 + inflation)years to retirement
Required Corpus = Future Expenses × 12 × (1 − (1+real_r)−years in retirement) / real_r

Where real_r = (1 + post-retirement return) / (1 + inflation) − 1

Required SIP = (Corpus − FV of existing savings) × r / (((1+r)n − 1) × (1+r))

Step 1 inflates today’s expenses to your retirement date. Step 2 computes the corpus that — invested in retirement — produces those inflation-adjusted monthly withdrawals for your remaining life expectancy.

Worked Example

Example: Age 30, retire at 60, live to 85. Today’s expenses $3,000/month. Inflation 5%, pre-retire return 11%, post-retire return 7%, existing savings $20,000. Required corpus ≈ $4.85M. Required monthly SIP ≈ $1,430. (Yes, this is why most people don’t hit retirement targets — they start late, save too little, or assume unrealistic returns.)

Levers You Can Pull

  • Start earlier. Starting at 25 vs 35 cuts the required SIP roughly in half, because you get an extra decade of compounding.
  • Cut monthly expenses. Every $500/month you don’t need in retirement saves roughly $100,000 in required corpus.
  • Step up the SIP. A 10% annual SIP increase can let you start with a smaller amount.
  • Delay retirement by 2–3 years. Triple effect: more years saving, more years compounding, fewer years drawing.
  • Be honest about returns. 12% pre-retirement is optimistic; 9–10% is more reliable. Better to save more and beat the plan than miss it.

Frequently Asked Questions

Should I include Social Security / EPF / pension?▾
Yes — model conservatively. Subtract your expected guaranteed income (in today’s dollars, inflated to retirement) from required monthly expenses before running this calculator. Many retirees underestimate the gap because they assume government pensions will keep pace with inflation.
What return rate should I assume post-retirement?▾
Conservative — 6–8% for a 60/40 equity/debt portfolio. Sequence-of-returns risk hurts most in early retirement, so resist temptation to use 10%+.
How much do I need to retire ‘comfortably’?▾
Rule of thumb: 25–30× your annual expenses (the 4% safe withdrawal rule, with a buffer). For $36,000/year expenses, that’s $900K–$1.08M in today’s dollars — but you need much more in nominal terms by the time you retire.
What if I plan to FIRE (retire early)?▾
Use the FIRE Calculator instead — it accounts for much longer retirement periods (40+ years) and uses a stricter 3.0–3.5% withdrawal rate.

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