Use this mirror calculator tool to quickly find out the cost of a custom-sized mirror for your space.

**Modified Internal Rate of Return (MIRR) Calculator**

## How to Use the Calculator

Enter the series of cash flows separated by commas in the “Cash Flows” field, starting with your initial investment (which should be a negative number, e.g., -1000).

Input the finance rate (the cost of borrowing the funds for the investment) as a percentage in the “Finance Rate” field.

Enter the reinvestment rate (the rate at which you can reinvest cash inflows) as a percentage in the “Reinvestment Rate” field.

Click the “Calculate” button to see the MIRR result in the “Result” field as a percentage.

## How the Calculator Works

The calculator computes the MIRR based on the three sets of data:

**Cash Flows:**The sequence of cash inflows and outflows over the investment period.**Finance Rate:**The cost of funds or rate of return required for investments.**Reinvestment Rate:**The returns generated from reinvesting the cash flows.

The calculation considers the present value of negative cash flows (outflows) adjusted by the finance rate and the future value of positive cash flows (inflows) reinvested at the reinvestment rate. The calculator then iteratively searches for the rate at which these present and future values match, yielding the MIRR.

## Limitations

The calculator assumes cash flows occur at regular intervals and that all reinvestments are made at the specified reinvestment rate. Cash flows must be entered in the correct order, and the first value must be negative, representing the initial investment.

The MIRR calculation requires a consistent pattern of inflows and outflows. It may not provide a reliable rate of return if the cash flow pattern is highly irregular or if additional investments are made during the investment period.

Lastly, the numeric solution has a set tolerance and number of iterations for finding the MIRR. In certain cases, if the MIRR does not converge within these limits, the calculator will show an error message.