Work backward from a retirement duration
This calculator answers a specific question: what equal monthly withdrawal would take a starting balance to zero over a chosen duration? It is a cash-flow calculation. It is not a recommendation to spend that amount or a prediction of investment performance.
Set the duration in whole years. The tool calculates twelve withdrawals per year and uses the unrounded monthly amount for the projection. Displayed currency is rounded to the nearest dollar; an actual payment rounded up can use up the balance earlier.
The sustainable-withdrawal formula
B = starting balance
r = monthly return
n = years × 12
Here “sustainable” means sustainable only inside this fixed-return model. At zero return, W = B ÷ n. For beginning-of-month withdrawals, divide W by (1 + r). With inflation adjustment on, r is the effective monthly real return, so the payment is expressed in today’s purchasing power.
Worked example: $360,000 over 30 years
With no return and no inflation adjustment, 30 years contains 360 monthly payments. A $360,000 starting balance therefore funds $1,000 per month. At a positive assumed real return the model permits a larger payment; at a negative real return it permits a smaller one.
Keep the target separate from the decision
Using a longer duration spreads the same starting balance over more withdrawals. Leaving a reserve, accounting for taxes, and choosing an investment strategy require decisions outside this calculator. Test lower returns and compare the result with your own spending estimate.
If you already know the amount you want to withdraw, use how long will my money last? to estimate the resulting timeline.
Questions about this calculation
Is this amount a safe withdrawal rate?
No. It is the payment that mathematically exhausts a balance over your chosen duration under constant assumptions. It does not simulate market volatility or assign a probability of success.
What if I want to leave money at the end?
This calculator targets a zero ending balance. To reserve a fixed amount outside this calculation, exclude it from the starting balance; this does not model growth or inflation of the reserve.
How does inflation change the withdrawal?
With adjustment enabled, the result is a monthly amount in today’s dollars. The modeled cash withdrawal increases each month with inflation. Without adjustment, the same nominal amount is withdrawn each month.
Methodology and sources
As of October 25, 2026. The formula is the rearranged present value of a monthly annuity, derived in our methodology. The worked example is arithmetic, not a market assumption. See the financial disclaimer before using a scenario for planning.