How to use this calculator
- Enter starting amount, monthly contribution, nominal annual rate (%), number of months, annual spending in today’s money, annual inflation assumption (%), initial withdrawal rate assumption (%).
- Choose a display currency, then select Calculate. Results also update after a brief pause while you edit.
- Read the result with the assumptions below. Export details or save a second scenario to compare your choices.
Formula and method
Assumptions and limitations
The nominal return is divided by 12 for both starting savings and deposits. Contributions stay nominally constant. The withdrawal percentage is user-entered and is not a safe-income guarantee. No pension, tax or sequence-of-returns simulation is included.
Worked example
Starting with 1,000 and adding 100 for 12 months at 0% produces 2,200. Annual spending of 1,000 with 0% inflation and a 4% withdrawal assumption implies a target of 25,000.
What the result means
The funding gap compares a simplified target with projected savings. The initial withdrawal scenario does not establish how long the money will last.
Common questions
Is the withdrawal rate safe?
No percentage is guaranteed safe. This result is a scenario for further planning.
Are returns consistent across the projection?
Yes. Both current savings and contributions use the same monthly rate convention.
Methodology and transparency
Calculation specification reviewed on 2026-10-14. Mathematical implementation is tested against independent reference fixtures. This does not imply review by a licensed financial professional. Read the testing and precision policy.
Background reference: openstax.org — financial method. FinanceMath implements its own calculator.