How Long Will My Money Last?
You have a pot of money — life savings, a property sale, a pension lump sum — and each month you withdraw a fixed amount to live on. The question that decides everything is simple: how many years does the pot last before it runs dry? This calculator simulates it month by month. The balance earns a return on what is left, then a withdrawal is taken out, and that withdrawal rises with inflation every year because the cost of living in Vietnam keeps climbing.
Two forces pull against each other. Investment growth — a savings deposit, a bond, a fund — adds to the balance, while the inflation-adjusted withdrawal drains it. If your real return (return minus inflation) is high enough relative to the rate you withdraw, the money can last indefinitely or even grow. If you withdraw too aggressively, the balance erodes and eventually hits zero faster than most people expect. Take 2.000.000.000 VND drawing 20.000.000 VND a month — a 12.0% first-year withdrawal rate — at an illustrative 6% return and 4% inflation: the pot lasts about 9 years 5 months, paying out 2.664.084.329 VND in total.
The tool above lets you enter your current balance, monthly withdrawal, an expected return and an inflation rate, then plots the balance declining year by year until it reaches zero. Keep in mind that the 6% and 4% figures are illustrative assumptions, not promises — Vietnamese deposit rates, fund returns and inflation all shift from year to year. Run several scenarios, especially a pessimistic one with a lower return and higher inflation, to see how robust your plan really is.
How the calculator works out how long your money lasts
A month-by-month simulation
Unlike a one-line formula, "how long will my money last" needs a month-by-month loop, because the withdrawal changes over time. Each month the tool does three things in order:
- Grow: multiply the balance by (1 + monthly return), where the monthly return is the annual return ÷ 12.
- Withdraw: subtract that month's withdrawal.
- Index to inflation: every 12 months, multiply the withdrawal by (1 + inflation) so it keeps its purchasing power.
| Symbol | Meaning |
|---|---|
| B | Current balance (starts at 2.000.000.000 VND in the example) |
| W | Monthly withdrawal (starts at 20.000.000 VND) |
| r_m | Monthly return = annual return ÷ 12 (6% ÷ 12) |
| g | Annual inflation, applied to W every 12 months (4%) |
The loop stops the first month the balance — after growth — cannot fund a full withdrawal. At that point the tool pays out whatever is left, sets the balance to zero, and reports the number of months survived. The year-by-year table below records the end-of-year balance, so every figure is reproducible.
When does money "last indefinitely"?
It comes down to real return versus withdrawal rate. Real return is roughly the annual return minus inflation (6 − 4 = 2% a year here). If your first-year withdrawal rate is below that real return, growth covers the withdrawals and the balance holds steady or grows — the tool flags it as sustainable. In the headline example the 12.0% withdrawal rate is above the ~2% real return, so the pot drains. This is the modern, inflation-aware version of the old "4% rule": the safe rate depends entirely on the return and inflation you assume.
What the model leaves out
The tool assumes a constant return and inflation for the whole horizon, growth spread evenly each month, and no taxes or fees. Real markets are volatile, and a run of bad years early on (sequence-of-returns risk) can drain a pot far faster than the average suggests. Treat the result as a planning scenario, not a precise prediction of the day you run out.
Worked example: 2.000.000.000 VND drawing 20.000.000 VND/month
Illustrative assumptions: a 6% annual return, 4% inflation (the withdrawal steps up each year), no taxes or fees.
| Milestone | End-of-year balance | Note |
|---|---|---|
| Start | 2.000.000.000 | Opening balance |
| Year 3 | 1.576.030.198 | Still substantial |
| Year 6 | 966.618.594 | Decline accelerating |
| Depleted | 0 | After 9 years 5 months |
Three things stand out.
- The drawdown accelerates toward the end. Early on the balance falls gently, but as the inflation-indexed withdrawal grows and the return is earned on an ever-smaller balance, the final years drop sharply — the pot is exhausted after 9 years 5 months.
- Inflation shortens the runway. The headline 3-billion example (3.000.000.000 VND drawing 25.000.000 VND/month) lasts 11 years 6 months with 4% inflation, but 15 years 4 months if you freeze the withdrawal and ignore inflation. That gap is the price of a rising cost of living.
- A lower withdrawal buys sustainability. Keep the same 3.000.000.000 VND but draw only 6.000.000 VND/month (a 2.4% rate, near the ~2% real return) and the balance barely moves over the full horizon — it effectively lasts forever.
In the smaller-pot scenario you withdraw 2.664.084.329 VND in total over 9 years 5 months. Enter your own numbers and stress-test a weaker market. FiMo also has retirement-withdrawal and FIRE calculators if you want a fuller retirement plan.
Frequently asked questions
How long will my money last if I withdraw a fixed amount each month?
It depends on four things: your starting balance, the monthly withdrawal, the return you earn and inflation. The tool simulates each month — the balance grows, the withdrawal is taken out, and the withdrawal rises with inflation every year. Illustrative example: 2.000.000.000 VND drawing 20.000.000 VND/month at 6% return and 4% inflation lasts about 9 years 5 months, paying out 2.664.084.329 VND in total.
Why does the calculator increase my withdrawal with inflation?
Because the cost of living rises every year, so a withdrawal that covers your expenses today will fall short next year. The tool steps the withdrawal up by your inflation rate annually to preserve purchasing power, and that shortens how long the money lasts. With 3.000.000.000 VND: at 4% inflation the pot lasts 11 years 6 months, but with inflation switched off (a frozen 25.000.000 VND/month) it lasts 15 years 4 months. Ignoring inflation is the classic mistake that makes people overestimate their runway.
When does my money last forever instead of running out?
When your real return — return minus inflation — is at least as high as your withdrawal rate. In the example real return is 6 − 4 = 2% a year. A withdrawal above that drains the pot; below it, growth covers the withdrawals and the balance holds or grows, which the tool flags as sustainable. Keeping 3.000.000.000 VND but drawing only 6.000.000 VND/month (a 2.4% rate, near the ~2% real return) makes it last effectively indefinitely.
Does the 4% rule apply if I live in Vietnam?
The 4% rule (withdraw 4% in year one, then rise with inflation) comes from historical US stock and bond data, so don't transplant it directly. What matters is your withdrawal rate versus the real return you genuinely expect from your own mix — VND deposits, bonds or funds. This calculator lets you set the return and inflation that fit your situation rather than relying on a single fixed percentage. Always test a low-return scenario for a margin of safety.
Are the 6% return and 4% inflation in the example guaranteed?
No. Both are illustrative assumptions chosen to keep the math easy to follow, not promises. Vietnamese deposit rates, fund returns and inflation all move year to year. The biggest danger for anyone living off withdrawals is a run of poor returns or high inflation early on — something a constant-rate model cannot capture. Enter figures you consider realistic, and always run a tougher scenario to stress-test your plan.
What does this drawdown model leave out?
It assumes a constant return and constant inflation for the whole horizon, growth spread evenly month by month, and no taxes or fees. Real returns are volatile, and a sequence of bad years early in retirement can exhaust a pot far sooner than the average implies — known as sequence-of-returns risk. Read the output as a planning scenario to compare options, not a precise forecast of the exact month your savings will run out.