How Magnus Works
Magnus is a retirement planning calculator built around one question: will your money actually last? This page explains the thinking behind it — and how it differs from a standard calculator.
The question every retiree is really asking
Most people approaching retirement — or already in it — have one real question behind all the numbers: will my money actually last? Not "what is my projected balance at 75" but "what happens if markets fall early, or inflation runs higher than expected, or I live longer than I planned for?"
Standard calculators cannot answer that honestly. They give you a single number based on fixed assumptions. Magnus was built to give you a realistic range of outcomes, not a false sense of certainty — making it a more useful retirement planning calculator for India, where inflation patterns, asset classes, and income structures differ significantly from Western planning tools. You can explore the Magnus Retirement Planner directly.
What traditional calculators get wrong
Most retirement calculators work in a straight line. They take your current savings, apply a fixed annual return, subtract a fixed annual withdrawal, and show you when the money runs out. This is mathematically simple and practically misleading.
Real markets do not move in straight lines. A 12% average return does not mean your portfolio grows 12% every year — it means some years are +28% and some are −18%. The sequence of those returns matters enormously, especially in the early years of retirement. A bad sequence early forces you to sell more units at low prices to fund withdrawals. You never fully recover those units, even if markets rebound strongly later.
Traditional calculators also treat inflation as a fixed number, ignore the difference between average and actual outcomes, and give you no sense of how much your plan depends on assumptions being exactly right. Magnus addresses all of these directly.
How Magnus is different
Monte Carlo simulation
Instead of projecting a single outcome, Magnus runs up to 2,000 simulations of your retirement — each with a different sequence of randomised annual returns drawn from a log-normal distribution. The result is not one number but a probability: in what percentage of simulated futures does your corpus survive to your target age? A plan with 90% success probability has survived intact in 9 out of 10 simulated futures. That is a meaningfully different way to understand retirement risk than a single projected balance.
Stress testing across five scenarios
Every time you calculate, Magnus automatically runs your plan through five adverse scenarios: base case, prolonged low returns, an early market crash in years one and two, high expense growth from faster inflation, and a medical cost spike from a chosen age. You see all five results side by side. This shows you not just whether your plan works under normal conditions, but how much it relies on things going reasonably well.
Inflation-adjusted, year-by-year projections
Magnus models inflation across up to five separate periods of retirement, because spending patterns change — many people spend more in active early years and less later. You can set a higher inflation rate for years one to ten and a lower rate for subsequent periods. Every withdrawal is inflated forward from today's money into the actual rupee figure your portfolio will need to fund in that year.
Income streams, lump-sum additions, and bucket withdrawal
Magnus models the full complexity of a real retirement plan. Pension income, rental income, or SCSS interest can be entered as separate income streams — including time-bounded ones that stop at a specific age. Expected lump sums such as PPF maturity or FD proceeds can be added to the portfolio at a future age. Bucket withdrawal lets safer assets fund near-term needs while equity grows untouched for longer. Each of these is reflected across every simulation path.
What Magnus shows you
The results are designed to give you a range of outcomes, not a false single answer.
Success probability — the percentage of simulated futures in which your corpus survives to your target age. 90% or above is generally considered robust. Below 70% warrants serious attention.
Fan chart — a visual showing the spread of portfolio balances across simulations over time. The wide band between the best and worst outcomes shows you how much uncertainty genuinely exists in your plan.
Survival age distribution — a histogram showing at what age the corpus runs out across all simulations. A cluster well past your target age means most futures end safely. A cluster close to or before your target age is a warning signal.
Safe withdrawal estimate — a binary search that finds the highest monthly withdrawal at which your corpus survives under your worst stress scenario. This is the most decision-relevant number Magnus produces.
Year-by-year table — a detailed row for every year of retirement showing your monthly expense, other income, net withdrawal from the portfolio, investment returns, and closing balance. When income streams are active, the table shows exactly how much they are reducing your portfolio draw that year.
What Magnus does not do
No financial advice. Magnus is a calculator. It models projections based on numbers you enter. It does not recommend products, funds, asset allocations, or courses of action. Results are only as reliable as your inputs and assumptions.
No tax modelling. All projections are pre-tax. Magnus does not account for LTCG on equity mutual funds, interest income tax on FDs, or slab-rate taxation on debt fund gains. For significant corpus sizes, the difference can be material. A qualified financial or tax advisor should review your plan before you act on it.
No product recommendations. Magnus does not suggest specific mutual funds, insurance products, or investment schemes. Return rate assumptions are entered by you based on your own holdings or expectations.
No joint planning. The current model plans for one person's corpus. Spouse income, joint assets, or blended household planning are not supported in this version.
Who this is built for
Magnus is designed for people who want to think seriously about retirement — not people looking for a quick estimate.
Five to fifteen years out, wanting a realistic view of whether their current savings trajectory will be sufficient.
Currently drawing from savings and wanting to understand whether their withdrawal rate is sustainable across realistic market conditions.
Pursuing financial independence on an accelerated timeline, with complex income and expense structures that standard calculators cannot model.
Individuals comfortable entering their own return assumptions, fund allocations, and inflation estimates — and interpreting probability-based outputs.
Magnus requires detailed inputs — that is intentional. Accurate projections require accurate data. If you want a rough number in thirty seconds, a simpler tool will serve you better. If you want to understand your actual risk, Magnus is built for that.
Ready to see your numbers?
Magnus is free to use. All calculations run privately on your device — nothing is uploaded to any server.