Enter your initial savings, monthly income, monthly expenses, and annual rate of return into the calculator to estimate how long your money will last (assuming these values stay constant over time).

How Long Will My Money Last Calculator

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How Long Will My Money Last Formula

The following equations estimate how long your money will last under a simplified model with constant monthly income and expenses and a constant annual rate of return (compounded monthly). If income is greater than or equal to expenses, the funds do not deplete under this model.

HL =
\begin{cases}
\dfrac{IS}{ME-MI}, & R=0 \\
\dfrac{\ln\!\left(\dfrac{ME-MI}{(ME-MI)-IS\cdot i}\right)}{\ln(1+i)}, & R>0
\end{cases}
\quad \text{where } i=\dfrac{R}{100\cdot 12}
  • Where HL is how long your money will last (months)
  • IS is the initial savings ($)
  • MI is the monthly income ($/month)
  • ME is the monthly expenses ($/month)
  • R is the annual rate of return (%)
  • i is the monthly interest rate (decimal), computed as R ÷ (100 × 12)

Notes: These formulas assume ME > MI (a net monthly withdrawal). If ME ≤ MI, your funds do not deplete under this simplified model. For the return-based case (R > 0), if IS × i ≥ (ME − MI), the monthly return is enough to cover the shortfall and the balance does not trend toward zero.

What Is the “How Long Will My Money Last” Calculation?

Definition:

How long your money will last typically refers to the number of months or years you can continue to meet your expenses before running out of funds. It depends on your starting savings, your ongoing income and expenses, and (if applicable) any investment return you earn on the remaining balance.

How to Calculate How Long Your Money Will Last

Example Problem:

The following example outlines the steps and information needed to calculate how long your money will last.

First, determine your monthly net outflow or inflow. In this example, the monthly income is $3,000, and monthly expenses are $4,000, so the net outflow is $1,000 per month.

Next, determine your initial savings. In this example, there is $50,000 in savings.

Finally, calculate how long your money will last. For simplicity, assume a 0% annual rate of return (R = 0), so the calculation reduces to:

HL = IS / (ME – MI)

HL = $50,000 / ($4,000 – $3,000)

HL = 50 months (approximately 4.17 years)

FAQ

How does a rate of return affect how long my money will last?

When your savings or investments earn returns, your money can last longer because part of your spending shortfall may be covered by the interest or gains on your remaining balance. A higher rate of return generally extends the duration before funds are depleted (assuming all else stays constant).

Should I include inflation in my calculations?

Yes, factoring in inflation is important. Rising prices can increase your expenses over time, thereby reducing how long your savings may last if your income does not keep pace. This calculator assumes fixed dollar amounts, so you would need to adjust your inputs over time to model inflation.

What can I do to make my money last longer?

Cutting unnecessary expenses, increasing your earning potential, and investing wisely to pursue appropriate returns can all help your money last for a longer duration.