A practice carrying 400 frames at $40 average wholesale has $16,000 sitting on the board, which rarely gets flagged in a budget meeting. But if half of those frames have been there longer than six months and a quarter have not moved in over a year, the carrying cost is higher than the balance sheet reflects, and the optical margin in the monthly financials is telling you less than you might think.

Frame boards are working capital. The distinction matters because working capital that turns slowly is capital that is not working hard enough, and the frames that stopped moving two seasons ago are the clearest sign that something in the buying process has drifted.

The metric is frame inventory turns: how many times per year your entire frame inventory sells through and gets replaced. A well-run optical dispensary targets 2 to 3 turns per year, a range cited consistently in optometry practice management literature including Review of Optometric Business and Optometric Management. Below 1.5 turns, you have an aging problem worth diagnosing.

Dollar figures and illustrative calculations in this article are meant to show the math, not to represent any specific practice. Your numbers will differ based on frame count, mix, and the wholesale costs your vendors charge.

How to Measure Whether Your Frame Board Is Working

The calculation needs two numbers from your financial statements: your annual frame cost of goods sold, and your average frame inventory value.

Turn rate = Annual frame COGS ÷ Average frame inventory value

If your optical sold $90,000 in frames at cost last year and your average frame inventory was $45,000, your turn rate is 2.0. Each frame, on average, sells roughly every six months.

To get the average inventory value, add your beginning-of-year and end-of-year frame inventory values and divide by two. For a more accurate picture, average the monthly snapshots if your accounting is tracking it that way.

What the numbers mean in dollars

At a 2.0 turn rate, the average frame sits on your board for six months before selling. At 1.0, twelve months. For a practice carrying $20,000 in frame inventory at a 1.0 turn rate, roughly $10,000 of that is on the board right now and will stay there, on average, for another six months before it earns anything.

Below 1.5 turns, a meaningful share of frames are genuinely stuck, not just slow. Frames in the 18 to 24 month range stop getting recommended in the dispensing conversation. They take up display space that newer arrivals need, and the markdown required to clear them grows the longer they stay. The cost compounds quietly.

This is also where the two-margin structure of a practice matters. The optical margin and the exam revenue behave differently and should be read separately. If you want to see how they interact and where frame inventory fits into the broader picture, the two-margins article covers the setup for a practice with both an exam side and a dispensary.

What Causes Frames to Age

The most common cause is not a bad buying decision in isolation. It is a buying pattern that runs on the vendor rep's calendar rather than the practice's actual sales data.

Most vendor reps visit quarterly or semi-annually, arriving prepared with new collections and trunk show promotions, often with volume discounts tied to order size. The practice ends up buying frames because the rep arrived with a good offer, not because the board needed what the rep brought. Over two or three years of this, the board fills up. Display space gets shared across too many styles. The newest arrivals claim the best placement; older frames drift toward the back rows and stay there.

Depth versus width

A frame board stocked deep, three or four of the same style in different colors, looks well-supplied but turns slowly by design. Patients rarely need the same frame twice. A board that is wide in selection and shallow in depth, mostly one or two of each style, turns faster because patients are choosing from more distinct options with less redundancy.

Vendors are generally incentivized to recommend depth because it drives volume. The buying discipline has to come from the practice, not from the rep conversation.

Style cycles

Fashion frames have a window, and it narrows faster than most practices account for. A trending frame from 18 months ago is not worthless, but it is harder to recommend with enthusiasm. Optical staff know this intuitively, and frames they are not excited about tend to get passed over during the dispensing conversation, sometimes without anyone deciding to do so.

A frame that sold at full price in year one typically needs a price promotion in year two. By month 18, the markdown required to clear it is usually larger than an earlier, smaller one would have been. That difference is a quiet margin drain that shows up in the optical COGS percentage before it is obvious anywhere else.

When Low Turns Are Not the Problem

Not every practice with a 1.5 turn rate has a management problem worth losing sleep over.

A new practice in its first two years is still building a patient base and a dispensing reputation. Carrying more inventory than current sales justify can be a reasonable investment in selection depth while the clientele develops. A boutique optical with a curated collection at $150 to $200 average wholesale may legitimately turn slower because those frames are more considered purchases, and the economics at that price point hold up differently.

The useful question is whether the turn rate is where it is by design or by drift. A conscious decision to carry more inventory for a specific reason is a business call. A turn rate that slipped from 2.0 to 1.2 over 18 months without a corresponding change in strategy is drift, and it is worth understanding before it continues for another 18.

The Open-to-Buy Approach

Open-to-buy (OTB) is a monthly purchasing budget you set before the vendor rep arrives.

The calculation starts with last month's frame cost of goods sold, which is the baseline for what your board consumed. Add any planned adjustments for an upcoming promotion or seasonal demand. Then compare your current frame inventory value against your target. If you are above target, your OTB budget is smaller than last month's sales, letting the board work down. If you are below target, you have room to spend more.

A simplified illustrative version:

  • Last month's frame COGS: $7,500
  • Target frame inventory value: $40,000
  • Current frame inventory value: $43,500 (over by $3,500)
  • OTB this month: $7,500 minus $3,500 = $4,000

With that number in hand before the rep arrives, the question shifts from "how many of these should I take" to "which of these do I want within my budget." For a smaller practice, the calculation takes about five minutes if the financial data is organized to support it.

The target inventory level itself is derived from the turn rate you are trying to maintain. If your frame COGS runs about $7,500 per month and you want a 2.0 turn rate, your target inventory is roughly $45,000 ($90,000 annual COGS divided by 2). That anchor is what keeps the OTB discipline honest over time.

What Your Monthly Financial Statements Should Show

The monthly financial statements from your bookkeeping should let you answer a few specific questions about the optical side of your practice without digging through raw data.

Is frame inventory growing or shrinking as a percentage of optical revenue over the last three to four months? What is the frame COGS percentage running compared to six months ago? Those two numbers, available directly from a well-structured set of financials, are the early warning system. When inventory climbs as a percent of optical revenue over several consecutive months, the turn rate is probably slipping before you have run the formal calculation.

For this to work, frame inventory needs to be tracked as its own line rather than folded into a broader cost-of-goods or optical supplies bucket. Without the separation, the turn rate calculation is not possible, and the month-over-month trends are invisible. If your current setup does not separate it, that is the practical first step: ask your accountant to reconfigure the chart of accounts so the data is clean going forward.

Our KPI white paper for optometry practice owners covers the monthly numbers that matter for practices like yours, including optical margin targets and how they compare to labor costs as a percent of revenue. You can download it free at caroandassociates.com/industries/optometrists/.

The broader optometry practice KPI benchmarks article also covers the specific ranges that most practice consultants reference when evaluating whether a practice is operating at healthy margins, which gives useful context for where your frame numbers sit relative to the exam side.

If your books do not currently support the frame turn calculation, ask your accountant to separate frame inventory in the chart of accounts. Run the calculation once that is in place, using the last 12 months of data. If the turn rate comes back below 1.5, you now have a specific number to bring into the conversation with your optical manager about what to change.

Questions owners ask about this

What is a good frame inventory turn rate for an optometry practice?

Most optical dispensaries target 2 to 3 turns per year. At 2 turns, the average frame sells roughly every six months. Below 1.5 turns is a warning sign: your average frame is sitting more than eight months before selling, and some are not moving at all. A new practice building its patient base may start lower, but an established practice below 1.5 should do an aging audit to see what is stuck.

How do I calculate my frame turn rate?

Divide your annual frame cost of goods sold by your average frame inventory value. If your optical sold $90,000 in frames at cost last year and you carry $45,000 in frame inventory on average, your turn rate is 2.0. You need both numbers from your financial statements. If your books combine frame COGS with contact lens or other optical costs, you cannot run this calculation cleanly without separating the data first.

When should I mark down aging frames?

Many practices use a 12-month trigger: any frame that has not sold in 12 months goes on promotion or goes back to the vendor through a return or exchange program. By 18 months, style risk is real and the markdown required to move the frame is typically larger than an earlier, smaller one would have been. Ask your vendor reps about rotation and return policies before frames hit that threshold, not after.

Does my accountant manage my frame inventory?

Your accountant records the inventory value and carries it on your balance sheet and in your cost of goods sold. The buying decisions and vendor relationships belong to you and your optical manager, as do the aging-frame markdowns. What good monthly financial statements can do is surface the early signals, specifically whether inventory is growing relative to optical revenue, so you catch a problem while it is still small.

What is open-to-buy and does it work for smaller optical dispensaries?

Open-to-buy is a monthly purchasing budget you set before the vendor rep arrives: based on last month's frame sales and your target inventory level, adjusted for any planned promotions, you calculate how much you can spend on new frames this period. It works at any scale. The discipline of knowing the number before the pitch is what prevents the slow over-buying that most aging inventory problems trace back to.