What is the SWP Calculator?
This SWP calculator estimates how long a starting corpus might last under a constant annual return assumption and monthly withdrawals. Enter a starting corpus, monthly withdrawal, planning annual return and an optional annual withdrawal increase. The result shows the estimated corpus runway and ending balance within a maximum 100-year simulation.
This is a simplified corpus-depletion model, not a mutual-fund unit or tax calculator. It does not track purchase lots, FIFO, capital gains, fund type, expense ratios, exit loads or withdrawal frequencies other than monthly. Taxes are not modeled; actual tax depends on the investment, purchase history, holding period and applicable rules.
The model assumes the entered return occurs consistently every month. Actual market returns vary, and the calculator does not model volatility or sequence-of-returns risk. Its runway is an illustration under the entered assumptions, not a guaranteed retirement duration.
How does it work?
The planning annual return is divided by 12 to produce a constant monthly rate. Each month the engine applies: Corpus after withdrawal = Opening corpus × (1 + monthly rate) − Monthly withdrawal. It repeats this sequence until the corpus reaches zero or the 1,200-month simulation cap is reached.
If an annual withdrawal increase is entered, the monthly withdrawal amount rises by that percentage once after every 12 withdrawals. It is not an inflation calculation, although you may use it as a simple planning proxy for rising spending. The engine does not offer quarterly or annual withdrawal frequencies and does not solve for a sustainable withdrawal amount or a chosen time horizon.
If the corpus remains positive at 1,200 months, the result says “100+ years under these assumptions.” That means only that the corpus survived the modeled horizon under a constant return; it does not mean the plan is safe, permanent or sustainable indefinitely.
Worked example
For a starting corpus of ₹50,00,000, a monthly withdrawal of ₹40,000, a planning annual return of 8% and no annual withdrawal increase, the calculator applies a constant monthly rate of 8% ÷ 12 before each withdrawal. The production engine estimates a runway of 270 months, shown as 22 years 6 months, with an ending balance of ₹0.
The example does not include taxes, fees, fund units, changing market returns or sequence risk. Changing the annual withdrawal increase from 0% would raise the monthly withdrawal once every 12 months and produce a different runway.
When to use this calculator
- 1Explore how a starting corpus changes under one monthly withdrawal and constant-return assumption.
- 2Compare different monthly withdrawal amounts while keeping the other planning assumptions explicit.
- 3Explore how increasing the withdrawal once per year changes the estimated corpus runway.
- 4Check whether a scenario depletes within the 100-year modeled horizon.
- 5Use a quick depletion estimate before reviewing a more detailed year-by-year scenario in Wealth Withdrawal.
Common mistakes to avoid
- ✕Treating the constant return as a forecast. Real returns vary and their sequence can materially change a withdrawal outcome.
- ✕Reading “100+ years under these assumptions” as permanently sustainable. The engine stops after 1,200 modeled months.
- ✕Assuming the output is after tax or fees. Neither is calculated, and no mutual-fund purchase lots are tracked.
- ✕Entering a quarterly or annual cash need as though the calculator supported that frequency. Every entered withdrawal is monthly.
- ✕Calling the annual withdrawal increase an inflation calculation. It simply raises the monthly withdrawal once after every 12 withdrawals.
Frequently asked questions
- What does this SWP calculator calculate?
- It estimates how many monthly withdrawals a starting corpus supports under a constant monthly return derived from your entered annual rate. It also reports the ending balance when the corpus depletes or reaches the 100-year cap.
- Does the calculator include tax on SWP withdrawals?
- No. Taxes are not modeled. Actual tax depends on the investment, purchase history, holding period and applicable tax rules. The calculator does not track mutual-fund units, purchase lots, FIFO or capital gains.
- Does the estimated runway account for market volatility?
- No. The model applies the same return every month and does not model market volatility or sequence-of-returns risk. The result is an illustration under your assumptions, not a guaranteed retirement duration.
- How does the annual withdrawal increase work?
- A positive percentage raises the monthly withdrawal once after every 12 withdrawals. You may use it as a simple proxy for rising spending, but the calculator does not separately calculate inflation.
- How is this different from Wealth Withdrawal?
- The generic SWP calculator provides a compact monthly depletion estimate. Wealth Withdrawal is a separate tool with a detailed year-by-year schedule and its own displayed timing convention. The tools are related but not identical.