What Is the Average Age of Inventory?

The average age of inventory is the average number of days it takes for a firm to sell off inventory. It is a metric that analysts use to determine the efficiency of sales. The average age of inventory is also referred to as days’ sales in inventory (DSI).

Formula and Calculation of Average Age of Inventory

The formula to calculate the average age of inventory is:


$\begin{aligned} &\text{Average Age of Inventory}= \frac{ C }{ G } \times 365 \\ &\textbf{where:} \\ &C = \text{The average cost of inventory at its present level} \\ &G = \text{The cost of goods sold (COGS)} \\ \end{aligned}$​Average Age of Inventory=GC​×365where:C=The average cost of inventory at its present levelG=The cost of goods sold (COGS)​

What the Average Age of Inventory Can Tell You

The average age of inventory tells the analyst how fast inventory is turning over at one company compared to another. The faster a company can sell inventory for a profit, the more profitable it is. However, a company could employ a strategy of maintaining higher levels of inventory for discounts or long-term planning efforts. While the metric can be used as a measure of efficiency, it should be confirmed with other measures of efficiency, such as gross profit margin, before making any conclusions.

The average age of inventory is a critical figure in industries with rapid sales and product cycles, such as the technology industry. A high average age of inventory can indicate that a firm is not properly managing its inventory or that it has an inventory that is difficult to sell.

The average age of inventory helps purchasing agents make buying decisions and managers make pricing decisions, such as discounting existing inventory to move products and increase cash flow. As a firm’s average age of inventory increases, its exposure to obsolescence risk also grows. Obsolescence risk is the risk that the value of inventory loses its value over time or in a soft market. If a firm is unable to move inventory, it can take an inventory write-off for some amount less than the stated value on a firm’s balance sheet.

Example of How to Use the Average Age of Inventory

An investor decides to compare two retail companies. Company A owns inventory valued at $100,000 and the COGS is $600,000. The average age of Company A’s inventory is calculated by dividing the average cost of inventory by the COGS and then multiplying the product by 365 days. The calculation is $100,000 divided by $600,000, multiplied by 365 days. The average age of inventory for Company A is 60.8 days. That means it takes the firm approximately two months to sell its inventory.

Conversely, Company B also owns inventory valued at $100,000, but the cost of inventory sold is $1 million, which reduces the average age of inventory to 36.5 days. On the surface, Company B is more efficient than Company A.

What Is Annual Turnover?

Annual turnover is the percentage rate at which something changes ownership over the course of a year. For a business, this rate could be related to its yearly turnover in inventories, receivables, payables, or assets.

In investments, a mutual fund or exchange-traded fund (ETF) turnover rate replaces its investment holdings on a yearly basis. Portfolio turnover is the comparison of assets under management (AUM) to the inflow, or outflow, of a fund’s holdings. The figure is useful to determine how actively the fund changes the underlying positions in its holdings. High figure turnover rates indicate an actively managed fund. Other funds are more passive and have a lower percentage of holding turnovers. An index fund is an example of a passive holding fund.

Calculating Annual Turnover

To calculate the portfolio turnover ratio for a given fund, first determine the total amount of assets purchased or sold (whichever happens to be greater), during the year. Then, divide that amount by the average assets held by the fund over the same year.


$\begin{aligned}&\text{portfolio turnover}\ =\ \frac{\operatorname{max}\begin{cases} \text{fund purchases}\\ \quad \text{fund sales}\end{cases}}{\text{average assets}}\end{aligned}$​portfolio turnover = average assetsmax{fund purchasesfund sales​​​

For example, if a mutual fund held $100 million in assets under management (AUM) and $75 million of those assets were liquidated at some point during the measurement period, the calculation is:


$\begin{aligned}&\frac{\$75\text{m}}{\$100\text{m}}=0.75\\&\textbf{where:}\\&\text{m}=\text{million}\end{aligned}$​$100m$75m​=0.75where:​

It is important to note that a fund turning over at 100% annually has not necessarily liquidated all positions with which it began the year. Instead, the complete turnover accounts for the frequent trading in and out of positions and the fact that sales of securities equal total AUM for the year. Also, using the same formula, the turnover rate is also measured by the number of securities bought in the measurement period.

Annualized Turnover in Investments

Annualized turnover is a future projection based on one month—or another shorter period of time—of investment turnover. For example, suppose that an ETF has a 5% turnover rate for the month of February. Using that figure, an investor may estimate annual turnover for the coming year by multiplying the one-month turnover by 12. This calculation provides an annualized holdings turnover rate of 60%.

Actively Managed Funds

Growth funds rely on trading strategies and stock selection from seasoned professional managers who set their sights on outperforming the index against which the portfolio benchmarks. Owning large equity positions is less about a commitment to corporate governance than it is a means to positive shareholder results. Managers who consistently beat the indices stay on the job and attract significant capital inflows.

While the passive versus active management argument persists, high volume approaches can realize moderate success. Consider the American Century Small Cap Growth fund (ANOIX), a four-star-rated Morningstar fund with a frantic 141% turnover rate (as of February 2021) that outperformed the S&P 500 Index considently over the last 15 years (through 2021).

Passively Managed Funds

Index funds, such as the Fidelity 500 Index Fund (FXAIX), adopt a buy-and-hold strategy. Following this system, the fund owns positions in equities as long as they remain components of the benchmark. The funds maintain a perfect, positive correlation to the index, and thus, the portfolio turnover rate is just 4%. Trading activity is limited to purchasing securities from inflows and infrequently selling issues removed from the index. More than 60% of the time, indices have historically outpaced managed funds.

Also, it is important to note, a high turnover rate judged in isolation is never an indicator of fund quality or performance. The Fidelity Spartan 500 Index Fund, after expenses, trailed the S&P 500 by 2.57% in 2020.

Annual Turnover in Business: Inventory Turnover

Businesses use several annual turnover metrics for understanding how well the business is running on a yearly basis. Inventory turnover measures how fast a company sells inventory and how analysts compare it to industry averages. A low turnover implies weak sales and possibly excess inventory, also known as overstocking. It may indicate a problem with the goods being offered for sale or be a result of too little marketing. A high ratio implies either strong sales or insufficient inventory. The former is desirable while the latter could lead to lost business. Sometimes a low inventory turnover rate is a good thing, such as when prices are expected to rise (inventory pre-positioned to meet fast-rising demand) or when shortages are anticipated.

The speed at which a company can sell inventory is a critical measure of business performance. Retailers that move inventory out faster tend to outperform. The longer an item is held, the higher its holding cost will be, and the fewer reasons consumers will have to return to the shop for new items.

What Is an Amortization Schedule?

Amortizing loans feature level payment amounts over the life of the loan, but with varying proportions of interest and principal making up each payment. A traditional mortgage is a prime example of such a loan.

A loan amortization schedule represents the complete table of periodic loan payments, showing the amount of principal and interest that comprise each level payment until the loan is paid off at the end of its term. Early in the schedule, the majority of each payment goes toward interest; later in the schedule, the majority of each payment begins to cover the loan’s remaining principal.

Understanding an Amortization Schedule

If you are taking out a mortgage or auto loan, your lender should provide you with a copy of your loan amortization schedule so you can see at a glance what the loan will cost and how the principal and interest will be broken down over its life.

In a loan amortization schedule, the percentage of each payment that goes toward interest diminishes a bit with each payment and the percentage that goes toward principal increases. Take, for example, a loan amortization schedule for a $165,000, 30-year fixed-rate mortgage with a 4.5% interest rate:

Amortization schedules can be customized based on your loan and your personal circumstances. With more sophisticated amortization calculators, like the templates you can find in Excel you can compare how making accelerated payments can accelerate your amortization. If for example, you are expecting an inheritance, or you get a set yearly bonus, you can use these tools to compare how applying that windfall to your debt can affect your loan’s maturity date and your interest cost over the life of the loan.

In addition to mortgages, car loans and personal loans are also amortizing for a term set in advance, at a fixed interest rate with a set monthly payment. The terms vary depending on the asset. Most conventional home loans are 15- or 30-year terms. Car owners often get an auto loan that will be repaid over five years or less. For personal loans, three years is a common term.

Formulas Used in Amortization Schedules

Borrowers and lenders use amortization schedules for installment loans that have payoff dates that are known at the time the loan is taken out, such as a mortgage or a car loan. There are specific formulas that are used to develop a loan amortization schedule. These formulas may be built into the software you are using, or you may need to set up your amortization schedule from scratch.

If you know the term of a loan and the total periodic payment amount, there is an easy way to calculate a loan amortization schedule without resorting to the use of an online amortization schedule or calculator. The formula to calculate the monthly principal due on an amortized loan is as follows:

Principal Payment = Total Monthly Payment – [Outstanding Loan Balance x (Interest Rate / 12 Months)]

To illustrate, imagine a loan has a 30-year term, a 4.5% interest rate, and a monthly payment of $1,266.71. Starting in month one, multiply the loan balance ($250,000) by the periodic interest rate. The periodic interest rate is one-twelfth of 4.5% (or 0.00375), so the resulting equation is $250,000 x 0.00375 = $937.50. The result is the first month’s interest payment. Subtract that amount from the periodic payment ($1,266.71 – $937.50) to calculate the portion of the loan payment allocated to the principal of the loan’s balance ($329.21).

To calculate the next month’s interest and principal payments, subtract the principal payment made in month one ($329.21) from the loan balance ($250,000) to get the new loan balance ($249,670.79), and then repeat the steps above to calculate which portion of the second payment is allocated to interest and which is allocated to the principal. You can repeat these steps until you have created an amortization schedule for the full life of the loan.

An Easier Way to Calculate an Amortization Schedule

Calculating an amortization schedule is as simple as entering the principal, interest rate, and loan term into a loan amortization calculator. But you can also calculate it by hand if you know the rate on the loan, the principal amount borrowed, and the loan term.

How to Calculate the Total Monthly Payment

Typically, the total monthly payment is specified by your lender when you take out a loan. However, if you are attempting to estimate or compare monthly payments based on a given set of factors, such as loan amount and interest rate, you may need to calculate the monthly payment as well.

If you need to calculate the total monthly payment for any reason, the formula is as follows:

Total Monthly Payment = Loan Amount [ i (1+i) ^ n / ((1+i) ^ n) – 1) ]

where:

• i = monthly interest rate. You’ll need to divide your annual interest rate by 12. For example, if your annual interest rate is 6%, your monthly interest rate will be .005 (.06 annual interest rate / 12 months).
• n = number of payments over the loan’s lifetime. Multiply the number of years in your loan term by 12. For example, a 30-year mortgage loan would have 360 payments (30 years x 12 months).

Using the same example from above, we will calculate the monthly payment on a $250,000 loan with a 30-year term and a 4.5% interest rate. The equation gives us $250,000 [(0.00375 (1.00375) ^ 360) / ((1.00375) ^ 360) – 1) ] = $1,266.71. The result is the total monthly payment due on the loan, including both principal and interest charges.

30-Year vs. 15-Year Amortization Table

If a borrower chooses a shorter amortization period for their mortgage—for example, 15 years—they will save considerably on interest over the life of the loan, and they will own the house sooner. That’s because they’ll make fewer payments for which interest will be amortized. Additionally, interest rates on shorter-term loans are often at a discount compared to longer-term loans.

There is a tradeoff, however. A shorter amortization window increases the monthly payment due on the loan. Short amortization mortgages are good options for borrowers who can handle higher monthly payments without hardship; they still involve making 180 sequential payments (15 years x 12 months).

It’s important to consider whether or not you can maintain that level of payment based on your current income and budget.

Using an amortization calculator can help you compare loan payments against potential interest savings for a shorter amortization to decide which option suits you best. Here’s what a $500,000 loan with a 6% interest rate would look like, with a hypothetical 30-year and 15-year schedule to compare:

What Is Add-On Interest?

Add-on interest is a method of calculating the interest to be paid on a loan by combining the total principal amount borrowed and the total interest due into a single figure, then multiplying that figure by the number of years to repayment. The total is then divided by the number of monthly payments to be made. The result is a loan that combines interest and principal into one amount due.

This method of calculating the payment on a loan is substantially more expensive for the borrower than the traditional simple interest calculation and is rarely used in consumer loans. Most loans use simple interest, where the interest charged is based on the amount of principal that is owed after each payment is made. Add-on interest loans may occasionally be used in short-term installment loans and in loans to subprime borrowers.

Understanding Add-On Interest

In simple interest loans, where the interest charged is based on the amount of principal that is owed after each payment is made, the payments may be identical in size from month to month, but that is because the principal paid increases over time while the interest paid decreases.

If the consumer pays off a simple interest loan early, the savings can be substantial. The number of interest payments that would have been attached to future monthly payments has been effectively erased.

But in an add-on interest loan, the amount owed is calculated upfront as a total of the principal borrowed plus annual interest at the stated rate, multiplied by the number of years until the loan is fully repaid. That total owed is then divided by the number of months of payments due in order to arrive at a monthly payment figure.

This means that the interest owed each month remains constant throughout the life of the loan. The interest owed is much higher, and, even if the borrower pays off the loan early, the interest charged will be the same.

Example of Add-On Interest

Say a borrower obtains a $25,000 loan at an 8% add-on interest rate that is to be repaid over four years.

• The amount of principal to be paid each month would be $520.83 ($25,000 / 48 months).
• The amount of interest owed each month would be $166.67 ($25,000 x 0.08 / 12).
• The borrower would be required to make payments of $687.50 each month ($520.83 + $166.67).
• The total interest paid would be $8,000 ($25,000 x 0.08 x 4).

Using a simple interest loan payment calculator, the same borrower with the same 8% interest rate on a $25,000 loan over four years would have required monthly payments of $610.32. The total interest due would be $3,586.62.

The borrower would pay $4,413.38 more for the add-on interest loan compared to the simple interest loan, that is, if the borrower did not pay off the loan early, reducing the total interest even more.

When researching a consumer loan, especially if you have poor credit, read the fine print carefully to determine whether the lender is charging you add-on interest. If that is the case, continue searching until you find a loan that charges simple interest.