Payback period is the time in which the initial outlay of an investment is expected to be recovered through the cash inflows generated by the investment. It is one of the simplest investment apprais-al techniques.

Since cash flow estimates are quite accurate for periods in the near future and relatively inaccurate for periods in distant future due to economic and operational uncertainties, payback period is an indicator of risk inherent in a project because it takes initial inflows into account and ignores the cash flows after the point at which the initial investment is recovered.

The formula to calculate the payback period of an investment depends on whether the periodic cash inflows from the project are even or uneven.

If the cash inflows are even (such as for investments in annuities), the formula to calculate payback period is:

Payback Period = Initial Investment / Net Cash Flow per Period

When cash inflows are uneven, we need to calculate the cumulative net cash flow for each period and then use the following formula:

Payback Period =A + (B/C)

Where,

A is the last period number with a negative cumulative cash flow;

B is the absolute value (i.e. value without negative sign) of cumulative net cash flow at the end of the period A; and

C is the total cash inflow during the period following period A

Cumulative net cash flow is the sum of inflows to date, minus the initial outflow.

- Payback Period | Formulas, Calculation & Examples (xplaind.com)

- CIPS study guide page 44-47

LO 1, AC 1.3