Your accountant tracks revenue. Your accountant tracks expenses. Your accountant produces a P&L that tells you whether you made money last month. What your accountant almost certainly does not track is flowthrough, which is the metric that tells you whether your restaurant is actually getting better.
Flowthrough is the percentage of incremental sales that converts to incremental profit. If your sales go up by $10,000 in a month, and your profit goes up by $2,500, your flowthrough is 25 percent. If your sales go up by $10,000 and your profit goes up by $500, your flowthrough is 5 percent. If your sales go up by $10,000 and your profit does not move, your flowthrough is zero.
That last scenario, zero flowthrough, is more common than most owners realize. And it is the most important warning sign that a restaurant's cost structure is broken.
Why flowthrough matters more than the P&L
The monthly P&L tells you where you ended up. Flowthrough tells you whether you are moving in the right direction. A restaurant can be unprofitable but improving, which is a very different situation from one that is unprofitable and getting worse. Flowthrough is the metric that distinguishes between the two.
Here is the underlying logic. A restaurant has two types of costs: fixed costs that do not change with sales volume (rent, management salaries, insurance, debt service) and variable costs that do change with sales volume (food cost, hourly labor, paper goods, credit card fees). When sales increase, variable costs increase proportionally, but fixed costs stay the same. The incremental sales should therefore generate a higher margin than your average margin, because the fixed costs are already covered.
If your flowthrough is low, it means your variable costs are rising faster than your sales, or your fixed costs are rising, or both. Either way, the business is getting less efficient as it grows, which is the opposite of what should happen.
The flowthrough calculation
To calculate flowthrough, you need two comparable periods: a base period and a comparison period. The comparison should be the same period from the prior year, or the prior quarter, or whatever comparison makes sense for your business seasonality.
Flowthrough = (Change in Profit) / (Change in Sales)
If your sales were $85,000 last month and $100,000 this month, and your profit was $5,000 last month and $8,500 this month, your flowthrough is $3,500 / $15,000 = 23 percent.
A healthy restaurant should generate flowthrough of 25 to 40 percent on incremental sales. Below 20 percent suggests a cost structure problem. Below 10 percent is a serious warning sign. Negative flowthrough, where profit declines as sales increase, means your cost structure is fundamentally broken.
The most common causes of low flowthrough
Low flowthrough usually has one of three causes.
The first is labor inefficiency. When sales increase, labor costs should increase at a lower rate, because you have some fixed labor (management, prep cooks, dishwashers) that does not scale linearly with sales. If your labor costs are increasing at the same rate as your sales, you are not capturing the operating leverage that higher volume should provide. This usually means your scheduling is not optimized, your management is not adjusting staffing to actual demand, or your labor model is too rigid.
The second is food cost creep. If your food cost percentage is rising as your sales increase, something is wrong with your purchasing, portioning, or waste management. Higher sales volume should give you more purchasing leverage, not less. If your food cost is going up as sales go up, you are losing control of the kitchen.
The third is overhead creep. Fixed costs that are not actually fixed. Marketing spend that increases with sales. Management bonuses that eat into the incremental profit. Maintenance deferred during slow periods that comes due when the restaurant is busier. These are all forms of overhead creep that suppress flowthrough.
What good flowthrough looks like in practice
At Metromedia Restaurant Group, where Rod built the performance analysis framework that underlies this work, flowthrough was one of the primary metrics for evaluating unit-level management performance. A unit manager who was growing sales but not generating adequate flowthrough was not managing the business well, regardless of how the top-line looked.
The discipline of tracking flowthrough forces a different conversation than the one most restaurant owners have with their accountants. Instead of "did we make money this month," the question becomes "are we getting more efficient as we grow, or are we just getting busier?" Those are very different questions with very different implications.
How to use flowthrough in your own business
Start by calculating your flowthrough for the last four quarters, comparing each quarter to the same quarter of the prior year. This gives you a trend line that is adjusted for seasonality.
If your flowthrough is consistently above 25 percent, your cost structure is working. If it is between 15 and 25 percent, you have room to improve but you are not in crisis. If it is below 15 percent, you have a cost structure problem that needs to be diagnosed and addressed.
The diagnosis starts with separating the flowthrough calculation by cost category. Calculate the change in food cost as a percentage of the change in sales. Do the same for labor, for direct operating expenses, and for overhead. The category with the worst flowthrough is where the problem lives.
This is the kind of analysis that a good restaurant accountant should be doing for you. If yours is not, it is worth having a conversation about adding it to your monthly reporting. The data is already in your P&L. The calculation is straightforward. The insight it provides is worth far more than the time it takes to produce it.
What the research says about cost structure and profitability
The National Restaurant Association's Restaurant Economic Insights tracks cost structure trends across the industry and consistently shows that labor and food cost together represent the largest variable cost exposure for independent operators. When the U.S. Bureau of Labor Statistics Employment Cost Index shows wage growth outpacing revenue growth, as it did in 2024 and 2025, flowthrough deteriorates across the industry. Operators who are tracking flowthrough can see this compression in real time and respond by adjusting scheduling, menu mix, or pricing. Operators who are only watching the monthly P&L often do not recognize the structural problem until it has been compounding for six to twelve months. Flowthrough is the early warning system that the P&L alone cannot provide.